C++提高编程C++ Advanced Programming

注意：这篇文章上次更新于1836天前，文章内容可能已经过时。

This article was last updated1836 days ago, the content may be outdated.

本阶段主要针对C++泛型编程和STL技术做详细讲解，探讨C++更深层的使用

模板

模板的概念

模板就是建立通用的模具，大大提高复用性

例如生活中的模板

一寸照片模板：

PPT模板：

模板的特点：

• 模板不可以直接使用，它只是一个框架
• 模板的通用并不是万能的

函数模板

• C++另一种编程思想称为 泛型编程 ，主要利用的技术就是模板

• C++提供两种模板机制:函数模板和类模板

函数模板语法

函数模板作用：

建立一个通用函数，其函数返回值类型和形参类型可以不具体制定，用一个虚拟的类型来代表。

语法：

This stage focuses on a detailed explanation of C++ generic programming and STL, exploring the deeper usage of C++

Templates

The Concept of Templates

A template is about creating a universal mold, which greatly improves reusability

For example, templates in daily life

One-inch photo template:

PPT template:

Features of templates:

• A template cannot be used directly; it is just a framework
• The universality of templates is not omnipotent

Function Templates

• Another programming idea of C++ is called generic programming, and the main technique used is templates

• C++ provides two template mechanisms: function templates and class templates

Function Template Syntax

The purpose of a function template:

To create a generic function whose return type and parameter types do not need to be specified concretely; instead, a virtual type is used to represent them.

Syntax:

template<typename T>
函数声明或定义

解释：

template — 声明创建模板

typename — 表面其后面的符号是一种数据类型，可以用class代替

T — 通用的数据类型，名称可以替换，通常为大写字母

示例：

Explanation:

template — declares the creation of a template

typename — indicates that the symbol following it is a data type, and can be replaced by class

T — a generic data type; the name can be replaced, usually an uppercase letter

Example:

//交换整型函数
void swapInt(int& a, int& b) {
	int temp = a;
	a = b;
	b = temp;
}

//交换浮点型函数
void swapDouble(double& a, double& b) {
	double temp = a;
	a = b;
	b = temp;
}

//利用模板提供通用的交换函数
template<typename T>
void mySwap(T& a, T& b)
{
	T temp = a;
	a = b;
	b = temp;
}

void test01()
{
	int a = 10;
	int b = 20;
	
	//swapInt(a, b);

	//利用模板实现交换
	//1、自动类型推导
	mySwap(a, b);

	//2、显示指定类型
	mySwap<int>(a, b);

	cout << "a = " << a << endl;
	cout << "b = " << b << endl;

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 函数模板利用关键字 template
• 使用函数模板有两种方式：自动类型推导、显示指定类型
• 模板的目的是为了提高复用性，将类型参数化

函数模板注意事项

注意事项：

• 自动类型推导，必须推导出一致的数据类型T,才可以使用

• 模板必须要确定出T的数据类型，才可以使用

示例：

Summary:

• Function templates use the keyword template
• There are two ways to use a function template: automatic type deduction and explicit type specification
• The purpose of a template is to improve reusability by parameterizing types

Notes on Function Templates

Notes:

• For automatic type deduction, a consistent data type T must be deduced before it can be used

• The data type of T must be determined before a template can be used

Example:

//利用模板提供通用的交换函数
template<class T>
void mySwap(T& a, T& b)
{
	T temp = a;
	a = b;
	b = temp;
}


// 1、自动类型推导，必须推导出一致的数据类型T,才可以使用
void test01()
{
	int a = 10;
	int b = 20;
	char c = 'c';

	mySwap(a, b); // 正确，可以推导出一致的T
	//mySwap(a, c); // 错误，推导不出一致的T类型
}


// 2、模板必须要确定出T的数据类型，才可以使用
template<class T>
void func()
{
	cout << "func 调用" << endl;
}

void test02()
{
	//func(); //错误，模板不能独立使用，必须确定出T的类型
	func<int>(); //利用显示指定类型的方式，给T一个类型，才可以使用该模板
}

int main() {

	test01();
	test02();

	system("pause");

	return 0;
}

总结：

• 使用模板时必须确定出通用数据类型T，并且能够推导出一致的类型

函数模板案例

案例描述：

• 利用函数模板封装一个排序的函数，可以对不同数据类型数组进行排序
• 排序规则从大到小，排序算法为选择排序
• 分别利用char数组和int数组进行测试

示例：

Summary:

• When using a template, the generic data type T must be determined, and a consistent type must be deducible

Function Template Case

Case description:

• Use a function template to encapsulate a sorting function that can sort arrays of different data types
• The sorting rule is from largest to smallest, and the sorting algorithm is selection sort
• Test with a char array and an int array respectively

Example:

//交换的函数模板
template<typename T>
void mySwap(T &a, T&b)
{
	T temp = a;
	a = b;
	b = temp;
}


template<class T> // 也可以替换成typename
//利用选择排序，进行对数组从大到小的排序
void mySort(T arr[], int len)
{
	for (int i = 0; i < len; i++)
	{
		int max = i; //最大数的下标
		for (int j = i + 1; j < len; j++)
		{
			if (arr[max] < arr[j])
			{
				max = j;
			}
		}
		if (max != i) //如果最大数的下标不是i，交换两者
		{
			mySwap(arr[max], arr[i]);
		}
	}
}
template<typename T>
void printArray(T arr[], int len) {

	for (int i = 0; i < len; i++) {
		cout << arr[i] << " ";
	}
	cout << endl;
}
void test01()
{
	//测试char数组
	char charArr[] = "bdcfeagh";
	int num = sizeof(charArr) / sizeof(char);
	mySort(charArr, num);
	printArray(charArr, num);
}

void test02()
{
	//测试int数组
	int intArr[] = { 7, 5, 8, 1, 3, 9, 2, 4, 6 };
	int num = sizeof(intArr) / sizeof(int);
	mySort(intArr, num);
	printArray(intArr, num);
}

int main() {

	test01();
	test02();

	system("pause");

	return 0;
}

总结：模板可以提高代码复用，需要熟练掌握

普通函数与函数模板的区别

普通函数与函数模板区别：

• 普通函数调用时可以发生自动类型转换（隐式类型转换）
• 函数模板调用时，如果利用自动类型推导，不会发生隐式类型转换
• 如果利用显示指定类型的方式，可以发生隐式类型转换

示例：

Summary: templates can improve code reuse and need to be mastered skillfully

Differences Between Ordinary Functions and Function Templates

Differences between ordinary functions and function templates:

• Ordinary functions can undergo automatic type conversion (implicit type conversion) when called
• Function templates will not undergo implicit type conversion when called with automatic type deduction
• Implicit type conversion can occur if the explicit type specification method is used

Example:

//普通函数
int myAdd01(int a, int b)
{
	return a + b;
}

//函数模板
template<class T>
T myAdd02(T a, T b)  
{
	return a + b;
}

//使用函数模板时，如果用自动类型推导，不会发生自动类型转换,即隐式类型转换
void test01()
{
	int a = 10;
	int b = 20;
	char c = 'c';
	
	cout << myAdd01(a, c) << endl; //正确，将char类型的'c'隐式转换为int类型  'c' 对应 ASCII码 99

	//myAdd02(a, c); // 报错，使用自动类型推导时，不会发生隐式类型转换

	myAdd02<int>(a, c); //正确，如果用显示指定类型，可以发生隐式类型转换
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：建议使用显示指定类型的方式，调用函数模板，因为可以自己确定通用类型T

普通函数与函数模板的调用规则

调用规则如下：

1. 如果函数模板和普通函数都可以实现，优先调用普通函数
2. 可以通过空模板参数列表来强制调用函数模板
3. 函数模板也可以发生重载
4. 如果函数模板可以产生更好的匹配,优先调用函数模板

示例：

Summary: it is recommended to call function templates using the explicit type specification method, because you can determine the generic type T yourself

Calling Rules for Ordinary Functions and Function Templates

The calling rules are as follows:

1. If both a function template and an ordinary function can do the job, the ordinary function is called first
2. An empty template argument list can force the function template to be called
3. Function templates can also be overloaded
4. If the function template can produce a better match, the function template is called first

Example:

//普通函数与函数模板调用规则
void myPrint(int a, int b)
{
	cout << "调用的普通函数" << endl;
}

template<typename T>
void myPrint(T a, T b) 
{ 
	cout << "调用的模板" << endl;
}

template<typename T>
void myPrint(T a, T b, T c) 
{ 
	cout << "调用重载的模板" << endl; 
}

void test01()
{
	//1、如果函数模板和普通函数都可以实现，优先调用普通函数
	// 注意 如果告诉编译器  普通函数是有的，但只是声明没有实现，或者不在当前文件内实现，就会报错找不到
	int a = 10;
	int b = 20;
	myPrint(a, b); //调用普通函数

	//2、可以通过空模板参数列表来强制调用函数模板
	myPrint<>(a, b); //调用函数模板

	//3、函数模板也可以发生重载
	int c = 30;
	myPrint(a, b, c); //调用重载的函数模板

	//4、 如果函数模板可以产生更好的匹配,优先调用函数模板
	char c1 = 'a';
	char c2 = 'b';
	myPrint(c1, c2); //调用函数模板
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：既然提供了函数模板，最好就不要提供普通函数，否则容易出现二义性

模板的局限性

局限性：

• 模板的通用性并不是万能的

例如：

Summary: since function templates are provided, it is best not to provide ordinary functions as well, otherwise ambiguity can easily occur

Limitations of Templates

Limitations:

• The universality of templates is not omnipotent

For example:

template<class T>
void f(T a, T b)
{ 
   	a = b;
   }

在上述代码中提供的赋值操作，如果传入的a和b是一个数组，就无法实现了

再例如：

In the assignment operation provided in the code above, if a and b passed in are arrays, it cannot be implemented

Another example:

template<class T>
void f(T a, T b)
{ 
   	if(a > b) { ... }
   }

在上述代码中，如果T的数据类型传入的是像Person这样的自定义数据类型，也无法正常运行

因此C++为了解决这种问题，提供模板的重载，可以为这些特定的类型提供具体化的模板

示例：

In the code above, if the data type passed for T is a custom data type like Person, it also cannot run normally

Therefore, to solve this problem, C++ provides template overloading, which can provide specialized templates for these specific types

Example:

#include<iostream>
using namespace std;

#include <string>

class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}
	string m_Name;
	int m_Age;
};

//普通函数模板
template<class T>
bool myCompare(T& a, T& b)
{
	if (a == b)
	{
		return true;
	}
	else
	{
		return false;
	}
}


//具体化，显示具体化的原型和定意思以template<>开头，并通过名称来指出类型
//具体化优先于常规模板
template<> bool myCompare(Person &p1, Person &p2)
{
	if ( p1.m_Name  == p2.m_Name && p1.m_Age == p2.m_Age)
	{
		return true;
	}
	else
	{
		return false;
	}
}

void test01()
{
	int a = 10;
	int b = 20;
	//内置数据类型可以直接使用通用的函数模板
	bool ret = myCompare(a, b);
	if (ret)
	{
		cout << "a == b " << endl;
	}
	else
	{
		cout << "a != b " << endl;
	}
}

void test02()
{
	Person p1("Tom", 10);
	Person p2("Tom", 10);
	//自定义数据类型，不会调用普通的函数模板
	//可以创建具体化的Person数据类型的模板，用于特殊处理这个类型
	bool ret = myCompare(p1, p2);
	if (ret)
	{
		cout << "p1 == p2 " << endl;
	}
	else
	{
		cout << "p1 != p2 " << endl;
	}
}

int main() {

	test01();

	test02();

	system("pause");

	return 0;
}

总结：

• 利用具体化的模板，可以解决自定义类型的通用化
• 学习模板并不是为了写模板，而是在STL能够运用系统提供的模板

类模板

类模板语法

类模板作用：

• 建立一个通用类，类中的成员 数据类型可以不具体制定，用一个虚拟的类型来代表。

语法：

Summary:

• Using specialized templates can solve the generalization problem of custom types
• Learning templates is not about writing templates, but about being able to use the templates provided by the system in STL

Class Templates

Class Template Syntax

The purpose of a class template:

• To create a generic class in which the data types of members do not need to be specified concretely; a virtual type is used to represent them.

Syntax:

template<typename T>
类

解释：

template — 声明创建模板

typename — 表面其后面的符号是一种数据类型，可以用class代替

T — 通用的数据类型，名称可以替换，通常为大写字母

示例：

Explanation:

template — declares the creation of a template

typename — indicates that the symbol following it is a data type, and can be replaced by class

T — a generic data type; the name can be replaced, usually an uppercase letter

Example:

#include <string>
//类模板
template<class NameType, class AgeType> 
class Person
{
public:
	Person(NameType name, AgeType age)
	{
		this->mName = name;
		this->mAge = age;
	}
	void showPerson()
	{
		cout << "name: " << this->mName << " age: " << this->mAge << endl;
	}
public:
	NameType mName;
	AgeType mAge;
};

void test01()
{
	// 指定NameType 为string类型，AgeType 为 int类型
	Person<string, int>P1("孙悟空", 999);
	P1.showPerson();
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：类模板和函数模板语法相似，在声明模板template后面加类，此类称为类模板

类模板与函数模板区别

类模板与函数模板区别主要有两点：

1. 类模板没有自动类型推导的使用方式
2. 类模板在模板参数列表中可以有默认参数

示例：

Summary: class templates and function templates have similar syntax; adding a class after the template declaration makes it a class template

Differences Between Class Templates and Function Templates

There are two main differences between class templates and function templates:

1. Class templates do not support automatic type deduction
2. Class templates can have default parameters in the template parameter list

Example:

#include <string>
//类模板
template<class NameType, class AgeType = int> 
class Person
{
public:
	Person(NameType name, AgeType age)
	{
		this->mName = name;
		this->mAge = age;
	}
	void showPerson()
	{
		cout << "name: " << this->mName << " age: " << this->mAge << endl;
	}
public:
	NameType mName;
	AgeType mAge;
};

//1、类模板没有自动类型推导的使用方式
void test01()
{
	// Person p("孙悟空", 1000); // 错误 类模板使用时候，不可以用自动类型推导
	Person <string ,int>p("孙悟空", 1000); //必须使用显示指定类型的方式，使用类模板
	p.showPerson();
}

//2、类模板在模板参数列表中可以有默认参数
void test02()
{
	Person <string> p("猪八戒", 999); //类模板中的模板参数列表 可以指定默认参数
	p.showPerson();
}

int main() {

	test01();

	test02();

	system("pause");

	return 0;
}

总结：

• 类模板使用只能用显示指定类型方式
• 类模板中的模板参数列表可以有默认参数

类模板中成员函数创建时机

类模板中成员函数和普通类中成员函数创建时机是有区别的：

• 普通类中的成员函数一开始就可以创建
• 类模板中的成员函数在调用时才创建

示例：

Summary:

• Class templates can only be used with explicit type specification
• The template parameter list of a class template can have default parameters

When Member Functions of Class Templates Are Created

The timing of member function creation differs between class templates and ordinary classes:

• Member functions of ordinary classes are created from the beginning
• Member functions of class templates are created only when called

Example:

class Person1
{
public:
	void showPerson1()
	{
		cout << "Person1 show" << endl;
	}
};

class Person2
{
public:
	void showPerson2()
	{
		cout << "Person2 show" << endl;
	}
};

template<class T>
class MyClass
{
public:
	T obj;

	//类模板中的成员函数，并不是一开始就创建的，而是在模板调用时再生成

	void fun1() { obj.showPerson1(); }
	void fun2() { obj.showPerson2(); }

};

void test01()
{
	MyClass<Person1> m;
	
	m.fun1();

	//m.fun2();//编译会出错，说明函数调用才会去创建成员函数
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：类模板中的成员函数并不是一开始就创建的，在调用时才去创建

类模板对象做函数参数

学习目标：

• 类模板实例化出的对象，向函数传参的方式

一共有三种传入方式：

1. 指定传入的类型 — 直接显示对象的数据类型
2. 参数模板化 — 将对象中的参数变为模板进行传递
3. 整个类模板化 — 将这个对象类型 模板化进行传递

示例：

Summary: the member functions of a class template are not created at the beginning, but only when they are called

Class Template Objects as Function Parameters

Learning objectives:

• How objects instantiated from a class template are passed to functions

There are three ways to pass them:

1. Specify the passed type — directly specify the data type of the object
2. Parameterize the parameters — turn the parameters of the object into templates for passing
3. Template the whole class — template the entire object type for passing

Example:

#include <string>
//类模板
template<class NameType, class AgeType = int> 
class Person
{
public:
	Person(NameType name, AgeType age)
	{
		this->mName = name;
		this->mAge = age;
	}
	void showPerson()
	{
		cout << "name: " << this->mName << " age: " << this->mAge << endl;
	}
public:
	NameType mName;
	AgeType mAge;
};

//1、指定传入的类型
void printPerson1(Person<string, int> &p) 
{
	p.showPerson();
}
void test01()
{
	Person <string, int >p("孙悟空", 100);
	printPerson1(p);
}

//2、参数模板化
template <class T1, class T2>
void printPerson2(Person<T1, T2>&p)
{
	p.showPerson();
	cout << "T1的类型为： " << typeid(T1).name() << endl;
	cout << "T2的类型为： " << typeid(T2).name() << endl;
}
void test02()
{
	Person <string, int >p("猪八戒", 90);
	printPerson2(p);
}

//3、整个类模板化
template<class T>
void printPerson3(T & p)
{
	cout << "T的类型为： " << typeid(T).name() << endl;
	p.showPerson();

}
void test03()
{
	Person <string, int >p("唐僧", 30);
	printPerson3(p);
}

int main() {

	test01();
	test02();
	test03();

	system("pause");

	return 0;
}

总结：

• 通过类模板创建的对象，可以有三种方式向函数中进行传参
• 使用比较广泛是第一种：指定传入的类型

类模板与继承

当类模板碰到继承时，需要注意一下几点：

• 当子类继承的父类是一个类模板时，子类在声明的时候，要指定出父类中T的类型
• 如果不指定，编译器无法给子类分配内存
• 如果想灵活指定出父类中T的类型，子类也需变为类模板

示例：

Summary:

• Objects created from a class template can be passed to functions in three ways
• The first way (specifying the passed type) is the most widely used

Class Templates and Inheritance

When a class template encounters inheritance, note the following points:

• When the parent class inherited by a child class is a class template, the child class must specify the type of T in the parent class when declaring
• If not specified, the compiler cannot allocate memory for the child class
• To flexibly specify the type of T in the parent class, the child class must also become a class template

Example:

template<class T>
class Base
{
	T m;
};

//class Son:public Base  //错误，c++编译需要给子类分配内存，必须知道父类中T的类型才可以向下继承
class Son :public Base<int> //必须指定一个类型
{
};
void test01()
{
	Son c;
}

//类模板继承类模板 ,可以用T2指定父类中的T类型
template<class T1, class T2>
class Son2 :public Base<T2>
{
public:
	Son2()
	{
		cout << typeid(T1).name() << endl;
		cout << typeid(T2).name() << endl;
	}
};

void test02()
{
	Son2<int, char> child1;
}


int main() {

	test01();

	test02();

	system("pause");

	return 0;
}

总结：如果父类是类模板，子类需要指定出父类中T的数据类型

类模板成员函数类外实现

学习目标：能够掌握类模板中的成员函数类外实现

示例：

Summary: if the parent class is a class template, the child class needs to specify the data type of T in the parent class

Out-of-Class Implementation of Class Template Member Functions

Learning objective: be able to implement class template member functions outside the class

Example:

#include <string>

//类模板中成员函数类外实现
template<class T1, class T2>
class Person {
public:
	//成员函数类内声明
	Person(T1 name, T2 age);
	void showPerson();

public:
	T1 m_Name;
	T2 m_Age;
};

//构造函数 类外实现
template<class T1, class T2>
Person<T1, T2>::Person(T1 name, T2 age) {
	this->m_Name = name;
	this->m_Age = age;
}

//成员函数 类外实现
template<class T1, class T2>
void Person<T1, T2>::showPerson() {
	cout << "姓名: " << this->m_Name << " 年龄:" << this->m_Age << endl;
}

void test01()
{
	Person<string, int> p("Tom", 20);
	p.showPerson();
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：类模板中成员函数类外实现时，需要加上模板参数列表

类模板分文件编写

学习目标：

• 掌握类模板成员函数分文件编写产生的问题以及解决方式

问题：

• 类模板中成员函数创建时机是在调用阶段，导致分文件编写时链接不到

解决：

• 解决方式1：直接包含.cpp源文件
• 解决方式2：将声明和实现写到同一个文件中，并更改后缀名为.hpp，hpp是约定的名称，并不是强制

示例：

person.hpp中代码：

Summary: when implementing class template member functions outside the class, the template parameter list must be added

Splitting Class Templates Across Files

Learning objectives:

• Understand the problems and solutions of writing class template member functions in separate files

Problem:

• Member functions of a class template are created at the call stage, which causes linking failures when split across files

Solutions:

• Solution 1: directly include the .cpp source file
• Solution 2: write the declaration and implementation in the same file and change the extension to .hpp; hpp is a convention, not a requirement

Example:

Code in person.hpp:

#pragma once
#include <iostream>
using namespace std;
#include <string>

template<class T1, class T2>
class Person {
public:
	Person(T1 name, T2 age);
	void showPerson();
public:
	T1 m_Name;
	T2 m_Age;
};

//构造函数 类外实现
template<class T1, class T2>
Person<T1, T2>::Person(T1 name, T2 age) {
	this->m_Name = name;
	this->m_Age = age;
}

//成员函数 类外实现
template<class T1, class T2>
void Person<T1, T2>::showPerson() {
	cout << "姓名: " << this->m_Name << " 年龄:" << this->m_Age << endl;
}

类模板分文件编写.cpp中代码

Code in the file that splits the class template across files (.cpp)

#include<iostream>
using namespace std;

//#include "person.h"
#include "person.cpp" //解决方式1，包含cpp源文件

//解决方式2，将声明和实现写到一起，文件后缀名改为.hpp
#include "person.hpp"
void test01()
{
	Person<string, int> p("Tom", 10);
	p.showPerson();
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：主流的解决方式是第二种，将类模板成员函数写到一起，并将后缀名改为.hpp

类模板与友元

学习目标：

• 掌握类模板配合友元函数的类内和类外实现

全局函数类内实现 - 直接在类内声明友元即可

全局函数类外实现 - 需要提前让编译器知道全局函数的存在

示例：

Summary: the mainstream solution is the second one: write the class template member functions together and change the extension to .hpp

Class Templates and Friends

Learning objectives:

• Master in-class and out-of-class implementation of friend functions with class templates

In-class implementation of a global function - just declare the friend directly inside the class

Out-of-class implementation of a global function - the compiler needs to know the existence of the global function in advance

Example:

#include <string>

//2、全局函数配合友元  类外实现 - 先做函数模板声明，下方在做函数模板定义，在做友元
template<class T1, class T2> class Person;

//如果声明了函数模板，可以将实现写到后面，否则需要将实现体写到类的前面让编译器提前看到
//template<class T1, class T2> void printPerson2(Person<T1, T2> & p); 

template<class T1, class T2>
void printPerson2(Person<T1, T2> & p)
{
	cout << "类外实现 ---- 姓名： " << p.m_Name << " 年龄：" << p.m_Age << endl;
}

template<class T1, class T2>
class Person
{
	//1、全局函数配合友元   类内实现
	friend void printPerson(Person<T1, T2> & p)
	{
		cout << "姓名： " << p.m_Name << " 年龄：" << p.m_Age << endl;
	}


	//全局函数配合友元  类外实现
	friend void printPerson2<>(Person<T1, T2> & p);

public:

	Person(T1 name, T2 age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}


private:
	T1 m_Name;
	T2 m_Age;

};

//1、全局函数在类内实现
void test01()
{
	Person <string, int >p("Tom", 20);
	printPerson(p);
}


//2、全局函数在类外实现
void test02()
{
	Person <string, int >p("Jerry", 30);
	printPerson2(p);
}

int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结：建议全局函数做类内实现，用法简单，而且编译器可以直接识别

类模板案例

案例描述: 实现一个通用的数组类，要求如下：

• 可以对内置数据类型以及自定义数据类型的数据进行存储
• 将数组中的数据存储到堆区
• 构造函数中可以传入数组的容量
• 提供对应的拷贝构造函数以及operator=防止浅拷贝问题
• 提供尾插法和尾删法对数组中的数据进行增加和删除
• 可以通过下标的方式访问数组中的元素
• 可以获取数组中当前元素个数和数组的容量

示例：

myArray.hpp中代码

Summary: it is recommended to implement global functions inside the class, which is simple to use and can be directly recognized by the compiler

Class Template Case

Case description: implement a generic array class with the following requirements:

• Can store data of built-in data types as well as custom data types
• Store the array data on the heap
• The capacity of the array can be passed in the constructor
• Provide the corresponding copy constructor and operator= to prevent shallow copy problems
• Provide tail insertion and tail deletion methods to add and remove data
• Support accessing array elements by subscript
• Can get the current number of elements and the capacity of the array

Example:

Code in myArray.hpp

#pragma once
#include <iostream>
using namespace std;

template<class T>
class MyArray
{
public:
    
	//构造函数
	MyArray(int capacity)
	{
		this->m_Capacity = capacity;
		this->m_Size = 0;
		pAddress = new T[this->m_Capacity];
	}

	//拷贝构造
	MyArray(const MyArray & arr)
	{
		this->m_Capacity = arr.m_Capacity;
		this->m_Size = arr.m_Size;
		this->pAddress = new T[this->m_Capacity];
		for (int i = 0; i < this->m_Size; i++)
		{
			//如果T为对象，而且还包含指针，必须需要重载 = 操作符，因为这个等号不是 构造 而是赋值，
			// 普通类型可以直接= 但是指针类型需要深拷贝
			this->pAddress[i] = arr.pAddress[i];
		}
	}

	//重载= 操作符  防止浅拷贝问题
	MyArray& operator=(const MyArray& myarray) {

		if (this->pAddress != NULL) {
			delete[] this->pAddress;
			this->m_Capacity = 0;
			this->m_Size = 0;
		}

		this->m_Capacity = myarray.m_Capacity;
		this->m_Size = myarray.m_Size;
		this->pAddress = new T[this->m_Capacity];
		for (int i = 0; i < this->m_Size; i++) {
			this->pAddress[i] = myarray[i];
		}
		return *this;
	}

	//重载[] 操作符  arr[0]
	T& operator [](int index)
	{
		return this->pAddress[index]; //不考虑越界，用户自己去处理
	}

	//尾插法
	void Push_back(const T & val)
	{
		if (this->m_Capacity == this->m_Size)
		{
			return;
		}
		this->pAddress[this->m_Size] = val;
		this->m_Size++;
	}

	//尾删法
	void Pop_back()
	{
		if (this->m_Size == 0)
		{
			return;
		}
		this->m_Size--;
	}

	//获取数组容量
	int getCapacity()
	{
		return this->m_Capacity;
	}

	//获取数组大小
	int	getSize()
	{
		return this->m_Size;
	}


	//析构
	~MyArray()
	{
		if (this->pAddress != NULL)
		{
			delete[] this->pAddress;
			this->pAddress = NULL;
			this->m_Capacity = 0;
			this->m_Size = 0;
		}
	}

private:
	T * pAddress;  //指向一个堆空间，这个空间存储真正的数据
	int m_Capacity; //容量
	int m_Size;   // 大小
};

类模板案例—数组类封装.cpp中

Code in the class template case - array class encapsulation (.cpp)

#include "myArray.hpp"
#include <string>

void printIntArray(MyArray<int>& arr) {
	for (int i = 0; i < arr.getSize(); i++) {
		cout << arr[i] << " ";
	}
	cout << endl;
}

//测试内置数据类型
void test01()
{
	MyArray<int> array1(10);
	for (int i = 0; i < 10; i++)
	{
		array1.Push_back(i);
	}
	cout << "array1打印输出：" << endl;
	printIntArray(array1);
	cout << "array1的大小：" << array1.getSize() << endl;
	cout << "array1的容量：" << array1.getCapacity() << endl;

	cout << "--------------------------" << endl;

	MyArray<int> array2(array1);
	array2.Pop_back();
	cout << "array2打印输出：" << endl;
	printIntArray(array2);
	cout << "array2的大小：" << array2.getSize() << endl;
	cout << "array2的容量：" << array2.getCapacity() << endl;
}

//测试自定义数据类型
class Person {
public:
	Person() {} 
		Person(string name, int age) {
		this->m_Name = name;
		this->m_Age = age;
	}
public:
	string m_Name;
	int m_Age;
};

void printPersonArray(MyArray<Person>& personArr)
{
	for (int i = 0; i < personArr.getSize(); i++) {
		cout << "姓名：" << personArr[i].m_Name << " 年龄： " << personArr[i].m_Age << endl;
	}

}

void test02()
{
	//创建数组
	MyArray<Person> pArray(10);
	Person p1("孙悟空", 30);
	Person p2("韩信", 20);
	Person p3("妲己", 18);
	Person p4("王昭君", 15);
	Person p5("赵云", 24);

	//插入数据
	pArray.Push_back(p1);
	pArray.Push_back(p2);
	pArray.Push_back(p3);
	pArray.Push_back(p4);
	pArray.Push_back(p5);

	printPersonArray(pArray);

	cout << "pArray的大小：" << pArray.getSize() << endl;
	cout << "pArray的容量：" << pArray.getCapacity() << endl;

}

int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结：

能够利用所学知识点实现通用的数组

STL初识

STL的诞生

• 长久以来，软件界一直希望建立一种可重复利用的东西

• C++的面向对象和泛型编程思想，目的就是复用性的提升

• 大多情况下，数据结构和算法都未能有一套标准,导致被迫从事大量重复工作

• 为了建立数据结构和算法的一套标准,诞生了STL

STL基本概念

• STL(Standard Template Library,标准模板库)
• STL 从广义上分为: 容器(container) 算法(algorithm) 迭代器(iterator)
• 容器和算法之间通过迭代器进行无缝连接。
• STL 几乎所有的代码都采用了模板类或者模板函数

STL六大组件

STL大体分为六大组件，分别是:容器、算法、迭代器、仿函数、适配器（配接器）、空间配置器

1. 容器：各种数据结构，如vector、list、deque、set、map等,用来存放数据。
2. 算法：各种常用的算法，如sort、find、copy、for_each等
3. 迭代器：扮演了容器与算法之间的胶合剂。
4. 仿函数：行为类似函数，可作为算法的某种策略。
5. 适配器：一种用来修饰容器或者仿函数或迭代器接口的东西。
6. 空间配置器：负责空间的配置与管理。

STL中容器、算法、迭代器

**容器：**置物之所也

STL容器就是将运用最广泛的一些数据结构实现出来

常用的数据结构：数组, 链表,树, 栈, 队列, 集合, 映射表 等

这些容器分为序列式容器和关联式容器两种:

​ 序列式容器:强调值的排序，序列式容器中的每个元素均有固定的位置。
​ 关联式容器:二叉树结构，各元素之间没有严格的物理上的顺序关系

**算法：**问题之解法也

有限的步骤，解决逻辑或数学上的问题，这一门学科我们叫做算法(Algorithms)

算法分为:质变算法和非质变算法。

质变算法：是指运算过程中会更改区间内的元素的内容。例如拷贝，替换，删除等等

非质变算法：是指运算过程中不会更改区间内的元素内容，例如查找、计数、遍历、寻找极值等等

**迭代器：**容器和算法之间粘合剂

提供一种方法，使之能够依序寻访某个容器所含的各个元素，而又无需暴露该容器的内部表示方式。

每个容器都有自己专属的迭代器

迭代器使用非常类似于指针，初学阶段我们可以先理解迭代器为指针

迭代器种类：

种类	功能	支持运算
输入迭代器	对数据的只读访问	只读，支持++、==、！=
输出迭代器	对数据的只写访问	只写，支持++
前向迭代器	读写操作，并能向前推进迭代器	读写，支持++、==、！=
双向迭代器	读写操作，并能向前和向后操作	读写，支持++、–，
随机访问迭代器	读写操作，可以以跳跃的方式访问任意数据，功能最强的迭代器	读写，支持++、–、[n]、-n、<、<=、>、>=

常用的容器中迭代器种类为双向迭代器，和随机访问迭代器

容器算法迭代器初识

了解STL中容器、算法、迭代器概念之后，我们利用代码感受STL的魅力

STL中最常用的容器为Vector，可以理解为数组，下面我们将学习如何向这个容器中插入数据、并遍历这个容器

vector存放内置数据类型

容器： vector

算法： for_each

迭代器： vector<int>::iterator

示例：

Summary:

You can implement a generic array using the knowledge points learned

Getting to Know STL

The Birth of STL

• For a long time, the software industry has wanted to build something reusable

• The object-oriented and generic programming ideas of C++ aim at improving reusability

• In most cases, data structures and algorithms lack a standard, forcing people to do a lot of repetitive work

• To establish a standard for data structures and algorithms, STL was born

STL Basic Concepts

• STL (Standard Template Library, standard template library)
• In a broad sense, STL is divided into: container, algorithm, iterator
• Containers and algorithms are seamlessly connected through iterators
• Almost all STL code uses template classes or template functions

The Six Major Components of STL

STL is roughly divided into six major components: containers, algorithms, iterators, functors, adapters, allocators

1. Containers: various data structures, such as vector, list, deque, set, map, etc., used to store data
2. Algorithms: various common algorithms, such as sort, find, copy, for_each, etc.
3. Iterators: act as the glue between containers and algorithms
4. Functors: behave like functions and can serve as a strategy for algorithms
5. Adapters: something used to modify the interfaces of containers, functors, or iterators
6. Allocators: responsible for space allocation and management

Containers, Algorithms, and Iterators in STL

Containers: the place where things are stored

STL containers implement the most widely used data structures

Common data structures: arrays, linked lists, trees, stacks, queues, sets, hash tables, etc.

These containers are divided into two types: sequential containers and associative containers:

​ Sequential containers: emphasize the ordering of values; every element in a sequential container has a fixed position
​ Associative containers: binary tree structures, where there is no strict physical order between elements

Algorithms: the solution to problems

The discipline of solving logical or mathematical problems with finite steps is called algorithms (Algorithms)

Algorithms are divided into: mutating algorithms and non-mutating algorithms

Mutating algorithms: operations that change the content of elements in a range during execution, such as copy, replace, delete, etc.

Non-mutating algorithms: operations that do not change the content of elements in a range, such as find, count, traverse, find extremes, etc.

Iterators: the glue between containers and algorithms

Provide a method to visit each element contained in a container in order without exposing the internal representation of the container

Every container has its own dedicated iterator

Iterators are used very much like pointers; at the beginner stage, we can understand iterators as pointers

Iterator types:

Type	Function	Supported operations
Input iterator	Read-only access to data	Read-only, supports ++, ==, !=
Output iterator	Write-only access to data	Write-only, supports ++
Forward iterator	Read/write operations, and can advance the iterator forward	Read/write, supports ++, ==, !=
Bidirectional iterator	Read/write operations, and can move forward and backward	Read/write, supports ++, –
Random access iterator	Read/write operations, can access any data by jumping, the most powerful iterator	Read/write, supports ++, --, [n], -n, <, <=, >, >=

The most common iterator types in containers are bidirectional iterators and random access iterators

First Look at Containers, Algorithms, and Iterators

After understanding the concepts of containers, algorithms, and iterators in STL, let us use code to feel the charm of STL

The most commonly used container in STL is Vector, which can be understood as an array. Next, we will learn how to insert data into this container and traverse it

vector Storing Built-in Data Types

Container: vector

Algorithm: for_each

Iterator: vector<int>::iterator

Example:

#include <vector>
#include <algorithm>

void MyPrint(int val)
{
	cout << val << endl;
}

void test01() {

	//创建vector容器对象，并且通过模板参数指定容器中存放的数据的类型
	vector<int> v;
	//向容器中放数据
	v.push_back(10);
	v.push_back(20);
	v.push_back(30);
	v.push_back(40);

	//每一个容器都有自己的迭代器，迭代器是用来遍历容器中的元素
	//v.begin()返回迭代器，这个迭代器指向容器中第一个数据
	//v.end()返回迭代器，这个迭代器指向容器元素的最后一个元素的下一个位置
	//vector<int>::iterator 拿到vector<int>这种容器的迭代器类型

	vector<int>::iterator pBegin = v.begin();
	vector<int>::iterator pEnd = v.end();

	//第一种遍历方式：
	while (pBegin != pEnd) {
		cout << *pBegin << endl;
		pBegin++;
	}

	
	//第二种遍历方式：
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << endl;
	}
	cout << endl;

	//第三种遍历方式：
	//使用STL提供标准遍历算法  头文件 algorithm
	for_each(v.begin(), v.end(), MyPrint);
}

int main() {

	test01();

	system("pause");

	return 0;
}

Vector存放自定义数据类型

学习目标：vector中存放自定义数据类型，并打印输出

示例：

Vector Storing Custom Data Types

Learning objective: store custom data types in vector and print them out

Example:

#include <vector>
#include <string>

//自定义数据类型
class Person {
public:
	Person(string name, int age) {
		mName = name;
		mAge = age;
	}
public:
	string mName;
	int mAge;
};
//存放对象
void test01() {

	vector<Person> v;

	//创建数据
	Person p1("aaa", 10);
	Person p2("bbb", 20);
	Person p3("ccc", 30);
	Person p4("ddd", 40);
	Person p5("eee", 50);

	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);
	v.push_back(p5);

	for (vector<Person>::iterator it = v.begin(); it != v.end(); it++) {
		cout << "Name:" << (*it).mName << " Age:" << (*it).mAge << endl;

	}
}


//放对象指针
void test02() {

	vector<Person*> v;

	//创建数据
	Person p1("aaa", 10);
	Person p2("bbb", 20);
	Person p3("ccc", 30);
	Person p4("ddd", 40);
	Person p5("eee", 50);

	v.push_back(&p1);
	v.push_back(&p2);
	v.push_back(&p3);
	v.push_back(&p4);
	v.push_back(&p5);

	for (vector<Person*>::iterator it = v.begin(); it != v.end(); it++) {
		Person * p = (*it);
		cout << "Name:" << p->mName << " Age:" << (*it)->mAge << endl;
	}
}


int main() {

	test01();
    
	test02();

	system("pause");

	return 0;
}

Vector容器嵌套容器

学习目标：容器中嵌套容器，我们将所有数据进行遍历输出

示例：

Vector Containers Nesting Containers

Learning objective: nest containers inside containers, and traverse and output all the data

Example:

#include <vector>

//容器嵌套容器
void test01() {

	vector< vector<int> >  v;

	vector<int> v1;
	vector<int> v2;
	vector<int> v3;
	vector<int> v4;

	for (int i = 0; i < 4; i++) {
		v1.push_back(i + 1);
		v2.push_back(i + 2);
		v3.push_back(i + 3);
		v4.push_back(i + 4);
	}

	//将容器元素插入到vector v中
	v.push_back(v1);
	v.push_back(v2);
	v.push_back(v3);
	v.push_back(v4);


	for (vector<vector<int>>::iterator it = v.begin(); it != v.end(); it++) {

		for (vector<int>::iterator vit = (*it).begin(); vit != (*it).end(); vit++) {
			cout << *vit << " ";
		}
		cout << endl;
	}

}

int main() {

	test01();

	system("pause");

	return 0;
}

STL- 常用容器

string容器

string基本概念

本质：

• string是C++风格的字符串，而string本质上是一个类

string和char * 区别：

• char * 是一个指针
• string是一个类，类内部封装了char*，管理这个字符串，是一个char*型的容器。

特点：

string 类内部封装了很多成员方法

例如：查找find，拷贝copy，删除delete 替换replace，插入insert

string管理char*所分配的内存，不用担心复制越界和取值越界等，由类内部进行负责

string构造函数

构造函数原型：

• string(); //创建一个空的字符串 例如: string str;
  string(const char* s); //使用字符串s初始化
• string(const string& str); //使用一个string对象初始化另一个string对象
• string(int n, char c); //使用n个字符c初始化

示例：

STL - Common Containers

string Container

string Basic Concepts

Essence:

• string is the C++ style string, and string is essentially a class

Differences between string and char:*

• char* is a pointer
• string is a class that internally wraps char*, manages this string, and is a char*-type container

Features:

The string class internally encapsulates many member methods

For example: find for searching, copy for copying, delete and replace, insert for inserting

string manages the memory allocated by char*, so there is no need to worry about copy overflow or out-of-bounds access; the class handles it internally

string Constructors

Constructor prototypes:

• string(); //create an empty string, e.g.: string str;
  string(const char* s); //initialize using string s
• string(const string& str); //initialize another string object using a string object
• string(int n, char c); //initialize with n characters c

Example:

#include <string>
//string构造
void test01()
{
	string s1; //创建空字符串，调用无参构造函数
	cout << "str1 = " << s1 << endl;

	const char* str = "hello world";
	string s2(str); //把c_string转换成了string

	cout << "str2 = " << s2 << endl;

	string s3(s2); //调用拷贝构造函数
	cout << "str3 = " << s3 << endl;

	string s4(10, 'a');
	cout << "str3 = " << s3 << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：string的多种构造方式没有可比性，灵活使用即可

string赋值操作

功能描述：

• 给string字符串进行赋值

赋值的函数原型：

• string& operator=(const char* s); //char*类型字符串 赋值给当前的字符串
• string& operator=(const string &s); //把字符串s赋给当前的字符串
• string& operator=(char c); //字符赋值给当前的字符串
• string& assign(const char *s); //把字符串s赋给当前的字符串
• string& assign(const char *s, int n); //把字符串s的前n个字符赋给当前的字符串
• string& assign(const string &s); //把字符串s赋给当前字符串
• string& assign(int n, char c); //用n个字符c赋给当前字符串

示例：

Summary: the various construction methods of string are not comparable; just use them flexibly

string Assignment Operations

Description:

• Assign values to a string

Assignment function prototypes:

• string& operator=(const char* s); //assign a char* type string to the current string
• string& operator=(const string &s); //assign string s to the current string
• string& operator=(char c); //assign a character to the current string
• string& assign(const char *s); //assign string s to the current string
• string& assign(const char *s, int n); //assign the first n characters of string s to the current string
• string& assign(const string &s); //assign string s to the current string
• string& assign(int n, char c); //assign n characters c to the current string

Example:

//赋值
void test01()
{
	string str1;
	str1 = "hello world";
	cout << "str1 = " << str1 << endl;

	string str2;
	str2 = str1;
	cout << "str2 = " << str2 << endl;

	string str3;
	str3 = 'a';
	cout << "str3 = " << str3 << endl;

	string str4;
	str4.assign("hello c++");
	cout << "str4 = " << str4 << endl;

	string str5;
	str5.assign("hello c++",5);
	cout << "str5 = " << str5 << endl;


	string str6;
	str6.assign(str5);
	cout << "str6 = " << str6 << endl;

	string str7;
	str7.assign(5, 'x');
	cout << "str7 = " << str7 << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

​ string的赋值方式很多，operator= 这种方式是比较实用的

string字符串拼接

功能描述：

• 实现在字符串末尾拼接字符串

函数原型：

• string& operator+=(const char* str); //重载+=操作符
• string& operator+=(const char c); //重载+=操作符
• string& operator+=(const string& str); //重载+=操作符
• string& append(const char *s); //把字符串s连接到当前字符串结尾
• string& append(const char *s, int n); //把字符串s的前n个字符连接到当前字符串结尾
• string& append(const string &s); //同operator+=(const string& str)
• string& append(const string &s, int pos, int n);//字符串s中从pos开始的n个字符连接到字符串结尾

示例：

Summary:

​ There are many ways to assign a string, and the operator= method is the most practical

string String Concatenation

Description:

• Concatenate strings at the end of a string

Function prototypes:

• string& operator+=(const char* str); //overload the += operator
• string& operator+=(const char c); //overload the += operator
• string& operator+=(const string& str); //overload the += operator
• string& append(const char *s); //connect string s to the end of the current string
• string& append(const char *s, int n); //connect the first n characters of string s to the end of the current string
• string& append(const string &s); //same as operator+=(const string& str)
• string& append(const string &s, int pos, int n); //connect n characters starting from pos in string s to the end of the string

Example:

//字符串拼接
void test01()
{
	string str1 = "我";

	str1 += "爱玩游戏";

	cout << "str1 = " << str1 << endl;
	
	str1 += ':';

	cout << "str1 = " << str1 << endl;

	string str2 = "LOL DNF";

	str1 += str2;

	cout << "str1 = " << str1 << endl;

	string str3 = "I";
	str3.append(" love ");
	str3.append("game abcde", 4);
	//str3.append(str2);
	str3.append(str2, 4, 3); // 从下标4位置开始 ，截取3个字符，拼接到字符串末尾
	cout << "str3 = " << str3 << endl;
}
int main() {

	test01();

	system("pause");

	return 0;
}

总结：字符串拼接的重载版本很多，初学阶段记住几种即可

string查找和替换

功能描述：

• 查找：查找指定字符串是否存在
• 替换：在指定的位置替换字符串

函数原型：

• int find(const string& str, int pos = 0) const; //查找str第一次出现位置,从pos开始查找
• int find(const char* s, int pos = 0) const; //查找s第一次出现位置,从pos开始查找
• int find(const char* s, int pos, int n) const; //从pos位置查找s的前n个字符第一次位置
• int find(const char c, int pos = 0) const; //查找字符c第一次出现位置
• int rfind(const string& str, int pos = npos) const; //查找str最后一次位置,从pos开始查找
• int rfind(const char* s, int pos = npos) const; //查找s最后一次出现位置,从pos开始查找
• int rfind(const char* s, int pos, int n) const; //从pos查找s的前n个字符最后一次位置
• int rfind(const char c, int pos = 0) const; //查找字符c最后一次出现位置
• string& replace(int pos, int n, const string& str); //替换从pos开始n个字符为字符串str
• string& replace(int pos, int n,const char* s); //替换从pos开始的n个字符为字符串s

示例：

Summary: there are many overloaded versions of string concatenation; just remember a few at the beginner stage

string Find and Replace

Description:

• Find: check whether the specified string exists
• Replace: replace the string at the specified position

Function prototypes:

• int find(const string& str, int pos = 0) const; //find the first occurrence of str, searching from pos
• int find(const char* s, int pos = 0) const; //find the first occurrence of s, searching from pos
• int find(const char* s, int pos, int n) const; //find the first occurrence of the first n characters of s from position pos
• int find(const char c, int pos = 0) const; //find the first occurrence of character c
• int rfind(const string& str, int pos = npos) const; //find the last occurrence of str, searching from pos
• int rfind(const char* s, int pos = npos) const; //find the last occurrence of s, searching from pos
• int rfind(const char* s, int pos, int n) const; //find the last occurrence of the first n characters of s from pos
• int rfind(const char c, int pos = 0) const; //find the last occurrence of character c
• string& replace(int pos, int n, const string& str); //replace n characters starting from pos with string str
• string& replace(int pos, int n,const char* s); //replace n characters starting from pos with string s

Example:

//查找和替换
void test01()
{
	//查找
	string str1 = "abcdefgde";

	int pos = str1.find("de");

	if (pos == -1)
	{
		cout << "未找到" << endl;
	}
	else
	{
		cout << "pos = " << pos << endl;
	}
	

	pos = str1.rfind("de");

	cout << "pos = " << pos << endl;

}

void test02()
{
	//替换
	string str1 = "abcdefgde";
	str1.replace(1, 3, "1111");

	cout << "str1 = " << str1 << endl;
}

int main() {

	//test01();
	//test02();

	system("pause");

	return 0;
}

总结：

• find查找是从左往后，rfind从右往左
• find找到字符串后返回查找的第一个字符位置，找不到返回-1
• replace在替换时，要指定从哪个位置起，多少个字符，替换成什么样的字符串

string字符串比较

功能描述：

• 字符串之间的比较

比较方式：

• 字符串比较是按字符的ASCII码进行对比

= 返回 0

> 返回 1

< 返回 -1

函数原型：

• int compare(const string &s) const; //与字符串s比较
• int compare(const char *s) const; //与字符串s比较

示例：

Summary:

• find searches from left to right, rfind from right to left
• find returns the position of the first character found; if not found, it returns -1
• When replacing, you need to specify the starting position, how many characters, and what string to replace with

String Comparison

Description:

• Compare strings

Comparison method:

• Strings are compared character by character according to their ASCII codes

= returns 0

> returns 1

< returns -1

Function prototypes:

• int compare(const string &s) const; //compare with string s
• int compare(const char *s) const; //compare with string s

Example:

//字符串比较
void test01()
{

	string s1 = "hello";
	string s2 = "aello";

	int ret = s1.compare(s2);

	if (ret == 0) {
		cout << "s1 等于 s2" << endl;
	}
	else if (ret > 0)
	{
		cout << "s1 大于 s2" << endl;
	}
	else
	{
		cout << "s1 小于 s2" << endl;
	}

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：字符串对比主要是用于比较两个字符串是否相等，判断谁大谁小的意义并不是很大

string字符存取

string中单个字符存取方式有两种

• char& operator[](int n); //通过[]方式取字符
• char& at(int n); //通过at方法获取字符

示例：

Summary: string comparison is mainly used to compare whether two strings are equal; determining which is bigger or smaller is not very meaningful

string Character Access

There are two ways to access a single character in a string

• char& operator[](int n); //get the character by [] method
• char& at(int n); //get the character by the at method

Example:

void test01()
{
	string str = "hello world";

	for (int i = 0; i < str.size(); i++)
	{
		cout << str[i] << " ";
	}
	cout << endl;

	for (int i = 0; i < str.size(); i++)
	{
		cout << str.at(i) << " ";
	}
	cout << endl;


	//字符修改
	str[0] = 'x';
	str.at(1) = 'x';
	cout << str << endl;
	
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：string字符串中单个字符存取有两种方式，利用 [ ] 或 at

string插入和删除

功能描述：

• 对string字符串进行插入和删除字符操作

函数原型：

• string& insert(int pos, const char* s); //插入字符串
• string& insert(int pos, const string& str); //插入字符串
• string& insert(int pos, int n, char c); //在指定位置插入n个字符c
• string& erase(int pos, int n = npos); //删除从Pos开始的n个字符

示例：

Summary: there are two ways to access a single character in a string: using [ ] or at

string Insert and Erase

Description:

• Insert and delete characters in a string

Function prototypes:

• string& insert(int pos, const char* s); //insert a string
• string& insert(int pos, const string& str); //insert a string
• string& insert(int pos, int n, char c); //insert n characters c at the specified position
• string& erase(int pos, int n = npos); //delete n characters starting from Pos

Example:

//字符串插入和删除
void test01()
{
	string str = "hello";
	str.insert(1, "111");
	cout << str << endl;

	str.erase(1, 3);  //从1号位置开始3个字符
	cout << str << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**插入和删除的起始下标都是从0开始

string子串

功能描述：

• 从字符串中获取想要的子串

函数原型：

• string substr(int pos = 0, int n = npos) const; //返回由pos开始的n个字符组成的字符串

示例：

Summary: the starting subscripts of insertion and deletion both start from 0

string Substrings

Description:

• Get the desired substring from a string

Function prototypes:

• string substr(int pos = 0, int n = npos) const; //return a string composed of n characters starting from pos

Example:

//子串
void test01()
{

	string str = "abcdefg";
	string subStr = str.substr(1, 3);
	cout << "subStr = " << subStr << endl;

	string email = "hello@sina.com";
	int pos = email.find("@");
	string username = email.substr(0, pos);
	cout << "username: " << username << endl;

}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**灵活的运用求子串功能，可以在实际开发中获取有效的信息

vector容器

vector基本概念

功能：

• vector数据结构和数组非常相似，也称为单端数组

vector与普通数组区别：

• 不同之处在于数组是静态空间，而vector可以动态扩展

动态扩展：

• 并不是在原空间之后续接新空间，而是找更大的内存空间，然后将原数据拷贝新空间，释放原空间

• vector容器的迭代器是支持随机访问的迭代器

vector构造函数

功能描述：

• 创建vector容器

函数原型：

• vector<T> v; //采用模板实现类实现，默认构造函数
• vector(v.begin(), v.end()); //将v[begin(), end())区间中的元素拷贝给本身。
• vector(n, elem); //构造函数将n个elem拷贝给本身。
• vector(const vector &vec); //拷贝构造函数。

示例：

Summary: flexibly using the substring function can obtain useful information in real development

vector Container

vector Basic Concepts

Features:

• The vector data structure is very similar to an array, also called a single-ended array

Differences between vector and ordinary arrays:

• The difference is that an array is static space, while vector can dynamically expand

Dynamic expansion:

• It does not continue new space after the original space, but finds a larger memory space, copies the original data to the new space, and frees the original space

• The iterators of vector containers support random access

vector Constructors

Description:

• Create a vector container

Function prototypes:

• vector<T> v; //implemented with a template class, default constructor
• vector(v.begin(), v.end()); //copy the elements in the [begin(), end()) range of v to itself
• vector(n, elem); //the constructor copies n elems to itself
• vector(const vector &vec); //copy constructor

Example:

#include <vector>

void printVector(vector<int>& v) {

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

void test01()
{
	vector<int> v1; //无参构造
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	printVector(v1);

	vector<int> v2(v1.begin(), v1.end());
	printVector(v2);

	vector<int> v3(10, 100);
	printVector(v3);
	
	vector<int> v4(v3);
	printVector(v4);
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**vector的多种构造方式没有可比性，灵活使用即可

vector赋值操作

功能描述：

• 给vector容器进行赋值

函数原型：

• vector& operator=(const vector &vec);//重载等号操作符

• assign(beg, end); //将[beg, end)区间中的数据拷贝赋值给本身。

• assign(n, elem); //将n个elem拷贝赋值给本身。

示例：

Summary: the various construction methods of vector are not comparable; just use them flexibly

vector Assignment Operations

Description:

• Assign values to a vector container

Function prototypes:

• vector& operator=(const vector &vec); //overload the assignment operator

• assign(beg, end); //copy and assign the data in the [beg, end) range to itself

• assign(n, elem); //copy and assign n elems to itself

Example:

#include <vector>

void printVector(vector<int>& v) {

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

//赋值操作
void test01()
{
	vector<int> v1; //无参构造
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	printVector(v1);

	vector<int>v2;
	v2 = v1;
	printVector(v2);

	vector<int>v3;
	v3.assign(v1.begin(), v1.end());
	printVector(v3);

	vector<int>v4;
	v4.assign(10, 100);
	printVector(v4);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结： vector赋值方式比较简单，使用operator=，或者assign都可以

vector容量和大小

功能描述：

• 对vector容器的容量和大小操作

函数原型：

• empty(); //判断容器是否为空

• capacity(); //容器的容量

• size(); //返回容器中元素的个数

• resize(int num); //重新指定容器的长度为num，若容器变长，则以默认值填充新位置。

  ​ //如果容器变短，则末尾超出容器长度的元素被删除。

• resize(int num, elem); //重新指定容器的长度为num，若容器变长，则以elem值填充新位置。

  ​ //如果容器变短，则末尾超出容器长度的元素被删除

示例：

Summary: vector assignment is relatively simple; you can use either operator= or assign

vector Capacity and Size

Description:

• Operations on the capacity and size of a vector container

Function prototypes:

• empty(); //check whether the container is empty

• capacity(); //the capacity of the container

• size(); //return the number of elements in the container

• resize(int num); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with default values

  //if the container becomes shorter, the elements beyond the container length at the end are deleted

• resize(int num, elem); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with elem values

  //if the container becomes shorter, the elements beyond the container length at the end are deleted

Example:

#include <vector>

void printVector(vector<int>& v) {

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

void test01()
{
	vector<int> v1;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	printVector(v1);
	if (v1.empty())
	{
		cout << "v1为空" << endl;
	}
	else
	{
		cout << "v1不为空" << endl;
		cout << "v1的容量 = " << v1.capacity() << endl;
		cout << "v1的大小 = " << v1.size() << endl;
	}

	//resize 重新指定大小 ，若指定的更大，默认用0填充新位置，可以利用重载版本替换默认填充
	v1.resize(15,10);
	printVector(v1);

	//resize 重新指定大小 ，若指定的更小，超出部分元素被删除
	v1.resize(5);
	printVector(v1);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 判断是否为空 — empty
• 返回元素个数 — size
• 返回容器容量 — capacity
• 重新指定大小 — resize

vector插入和删除

功能描述：

• 对vector容器进行插入、删除操作

函数原型：

• push_back(ele); //尾部插入元素ele
• pop_back(); //删除最后一个元素
• insert(const_iterator pos, ele); //迭代器指向位置pos插入元素ele
• insert(const_iterator pos, int count,ele);//迭代器指向位置pos插入count个元素ele
• erase(const_iterator pos); //删除迭代器指向的元素
• erase(const_iterator start, const_iterator end);//删除迭代器从start到end之间的元素
• clear(); //删除容器中所有元素

示例：

Summary:

• Check whether it is empty — empty
• Return the number of elements — size
• Return the capacity of the container — capacity
• Re-specify the size — resize

vector Insert and Erase

Description:

• Insert and delete operations on a vector container

Function prototypes:

• push_back(ele); //insert element ele at the tail
• pop_back(); //delete the last element
• insert(const_iterator pos, ele); //insert element ele at the position pointed by iterator pos
• insert(const_iterator pos, int count,ele); //insert count elements ele at the position pointed by iterator pos
• erase(const_iterator pos); //delete the element pointed by the iterator
• erase(const_iterator start, const_iterator end); //delete the elements between iterators start and end
• clear(); //delete all elements in the container

Example:

#include <vector>

void printVector(vector<int>& v) {

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

//插入和删除
void test01()
{
	vector<int> v1;
	//尾插
	v1.push_back(10);
	v1.push_back(20);
	v1.push_back(30);
	v1.push_back(40);
	v1.push_back(50);
	printVector(v1);
	//尾删
	v1.pop_back();
	printVector(v1);
	//插入
	v1.insert(v1.begin(), 100);
	printVector(v1);

	v1.insert(v1.begin(), 2, 1000);
	printVector(v1);

	//删除
	v1.erase(v1.begin());
	printVector(v1);

	//清空
	v1.erase(v1.begin(), v1.end());
	v1.clear();
	printVector(v1);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 尾插 — push_back
• 尾删 — pop_back
• 插入 — insert (位置迭代器)
• 删除 — erase （位置迭代器）
• 清空 — clear

vector数据存取

功能描述：

• 对vector中的数据的存取操作

函数原型：

• at(int idx); //返回索引idx所指的数据
• operator[]; //返回索引idx所指的数据
• front(); //返回容器中第一个数据元素
• back(); //返回容器中最后一个数据元素

示例：

Summary:

• Tail insertion — push_back
• Tail deletion — pop_back
• Insertion — insert (position iterator)
• Deletion — erase (position iterator)
• Clear — clear

vector Data Access

Description:

• Access operations on data in a vector

Function prototypes:

• at(int idx); //return the data pointed by index idx
• operator[]; //return the data pointed by index idx
• front(); //return the first data element in the container
• back(); //return the last data element in the container

Example:

#include <vector>

void test01()
{
	vector<int>v1;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}

	for (int i = 0; i < v1.size(); i++)
	{
		cout << v1[i] << " ";
	}
	cout << endl;

	for (int i = 0; i < v1.size(); i++)
	{
		cout << v1.at(i) << " ";
	}
	cout << endl;

	cout << "v1的第一个元素为： " << v1.front() << endl;
	cout << "v1的最后一个元素为： " << v1.back() << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 除了用迭代器获取vector容器中元素，[ ]和at也可以
• front返回容器第一个元素
• back返回容器最后一个元素

vector互换容器

功能描述：

• 实现两个容器内元素进行互换

函数原型：

• swap(vec); // 将vec与本身的元素互换

示例：

Summary:

• Besides using iterators to get elements in a vector container, [ ] and at also work
• front returns the first element of the container
• back returns the last element of the container

vector Swapping Containers

Description:

• Swap the elements of two containers

Function prototypes:

• swap(vec); //swap the elements of vec with its own elements

Example:

#include <vector>

void printVector(vector<int>& v) {

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

void test01()
{
	vector<int>v1;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	printVector(v1);

	vector<int>v2;
	for (int i = 10; i > 0; i--)
	{
		v2.push_back(i);
	}
	printVector(v2);

	//互换容器
	cout << "互换后" << endl;
	v1.swap(v2);
	printVector(v1);
	printVector(v2);
}

void test02()
{
	vector<int> v;
	for (int i = 0; i < 100000; i++) {
		v.push_back(i);
	}

	cout << "v的容量为：" << v.capacity() << endl;
	cout << "v的大小为：" << v.size() << endl;

	v.resize(3);

	cout << "v的容量为：" << v.capacity() << endl;
	cout << "v的大小为：" << v.size() << endl;

	//收缩内存
	vector<int>(v).swap(v); //匿名对象

	cout << "v的容量为：" << v.capacity() << endl;
	cout << "v的大小为：" << v.size() << endl;
}

int main() {

	test01();

	test02();

	system("pause");

	return 0;
}

总结：swap可以使两个容器互换，可以达到实用的收缩内存效果

vector预留空间

功能描述：

• 减少vector在动态扩展容量时的扩展次数

函数原型：

• reserve(int len);//容器预留len个元素长度，预留位置不初始化，元素不可访问。

示例：

Summary: swap can exchange two containers, and can achieve a practical memory shrinking effect

vector Reserving Space

Description:

• Reduce the number of expansions when vector dynamically expands its capacity

Function prototypes:

• reserve(int len); //reserve space for len elements; the reserved positions are not initialized and cannot be accessed

Example:

#include <vector>

void test01()
{
	vector<int> v;

	//预留空间
	v.reserve(100000);

	int num = 0;
	int* p = NULL;
	for (int i = 0; i < 100000; i++) {
		v.push_back(i);
		if (p != &v[0]) {
			p = &v[0];
			num++;
		}
	}

	cout << "num:" << num << endl;
}

int main() {

	test01();
    
	system("pause");

	return 0;
}

总结：如果数据量较大，可以一开始利用reserve预留空间

deque容器

deque容器基本概念

功能：

• 双端数组，可以对头端进行插入删除操作

deque与vector区别：

• vector对于头部的插入删除效率低，数据量越大，效率越低
• deque相对而言，对头部的插入删除速度回比vector快
• vector访问元素时的速度会比deque快,这和两者内部实现有关

deque内部工作原理:

deque内部有个中控器，维护每段缓冲区中的内容，缓冲区中存放真实数据

中控器维护的是每个缓冲区的地址，使得使用deque时像一片连续的内存空间

• deque容器的迭代器也是支持随机访问的

deque构造函数

功能描述：

• deque容器构造

函数原型：

• deque<T> deqT; //默认构造形式
• deque(beg, end); //构造函数将[beg, end)区间中的元素拷贝给本身。
• deque(n, elem); //构造函数将n个elem拷贝给本身。
• deque(const deque &deq); //拷贝构造函数

示例：

Summary: if the amount of data is large, you can use reserve to reserve space at the beginning

deque Container

deque Basic Concepts

Features:

• A double-ended array that supports insertion and deletion at both ends

Differences between deque and vector:

• vector has low efficiency for insertion and deletion at the head; the larger the data, the lower the efficiency
• deque, in comparison, is faster at inserting and deleting at the head than vector
• vector is faster than deque when accessing elements, which is related to their internal implementations

How deque works internally:

There is a central controller inside deque that maintains the contents of each buffer segment, and the buffers store the real data

The central controller maintains the addresses of each buffer, making deque behave like a contiguous memory space

• The iterators of deque containers also support random access

deque Constructors

Description:

• Constructing a deque container

Function prototypes:

• deque<T> deqT; //default construction form
• deque(beg, end); //the constructor copies the elements in the [beg, end) range to itself
• deque(n, elem); //the constructor copies n elems to itself
• deque(const deque &deq); //copy constructor

Example:

#include <deque>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}
//deque构造
void test01() {

	deque<int> d1; //无参构造函数
	for (int i = 0; i < 10; i++)
	{
		d1.push_back(i);
	}
	printDeque(d1);
	deque<int> d2(d1.begin(),d1.end());
	printDeque(d2);

	deque<int>d3(10,100);
	printDeque(d3);

	deque<int>d4 = d3;
	printDeque(d4);
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**deque容器和vector容器的构造方式几乎一致，灵活使用即可

deque赋值操作

功能描述：

• 给deque容器进行赋值

函数原型：

• deque& operator=(const deque &deq); //重载等号操作符

• assign(beg, end); //将[beg, end)区间中的数据拷贝赋值给本身。

• assign(n, elem); //将n个elem拷贝赋值给本身。

示例：

Summary: the construction methods of deque containers are almost the same as those of vector containers; use them flexibly

deque Assignment Operations

Description:

• Assign values to a deque container

Function prototypes:

• deque& operator=(const deque &deq); //overload the assignment operator

• assign(beg, end); //copy and assign the data in the [beg, end) range to itself

• assign(n, elem); //copy and assign n elems to itself

Example:

#include <deque>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}
//赋值操作
void test01()
{
	deque<int> d1;
	for (int i = 0; i < 10; i++)
	{
		d1.push_back(i);
	}
	printDeque(d1);

	deque<int>d2;
	d2 = d1;
	printDeque(d2);

	deque<int>d3;
	d3.assign(d1.begin(), d1.end());
	printDeque(d3);

	deque<int>d4;
	d4.assign(10, 100);
	printDeque(d4);

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：deque赋值操作也与vector相同，需熟练掌握

deque大小操作

功能描述：

• 对deque容器的大小进行操作

函数原型：

• deque.empty(); //判断容器是否为空

• deque.size(); //返回容器中元素的个数

• deque.resize(num); //重新指定容器的长度为num,若容器变长，则以默认值填充新位置。

  ​ //如果容器变短，则末尾超出容器长度的元素被删除。

• deque.resize(num, elem); //重新指定容器的长度为num,若容器变长，则以elem值填充新位置。

  ​ //如果容器变短，则末尾超出容器长度的元素被删除。

示例：

Summary: deque assignment operations are also the same as vector; you need to master them skillfully

deque Size Operations

Description:

• Operations on the size of a deque container

Function prototypes:

• deque.empty(); //check whether the container is empty

• deque.size(); //return the number of elements in the container

• deque.resize(num); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with default values

  //if the container becomes shorter, the elements beyond the container length at the end are deleted

• deque.resize(num, elem); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with elem values

  //if the container becomes shorter, the elements beyond the container length at the end are deleted

Example:

#include <deque>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}

//大小操作
void test01()
{
	deque<int> d1;
	for (int i = 0; i < 10; i++)
	{
		d1.push_back(i);
	}
	printDeque(d1);

	//判断容器是否为空
	if (d1.empty()) {
		cout << "d1为空!" << endl;
	}
	else {
		cout << "d1不为空!" << endl;
		//统计大小
		cout << "d1的大小为：" << d1.size() << endl;
	}

	//重新指定大小
	d1.resize(15, 1);
	printDeque(d1);

	d1.resize(5);
	printDeque(d1);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• deque没有容量的概念
• 判断是否为空 — empty
• 返回元素个数 — size
• 重新指定个数 — resize

deque 插入和删除

功能描述：

• 向deque容器中插入和删除数据

函数原型：

两端插入操作：

• push_back(elem); //在容器尾部添加一个数据
• push_front(elem); //在容器头部插入一个数据
• pop_back(); //删除容器最后一个数据
• pop_front(); //删除容器第一个数据

指定位置操作：

• insert(pos,elem); //在pos位置插入一个elem元素的拷贝，返回新数据的位置。

• insert(pos,n,elem); //在pos位置插入n个elem数据，无返回值。

• insert(pos,beg,end); //在pos位置插入[beg,end)区间的数据，无返回值。

• clear(); //清空容器的所有数据

• erase(beg,end); //删除[beg,end)区间的数据，返回下一个数据的位置。

• erase(pos); //删除pos位置的数据，返回下一个数据的位置。

示例：

Summary:

• deque has no concept of capacity
• Check whether it is empty — empty
• Return the number of elements — size
• Re-specify the count — resize

deque Insert and Erase

Description:

• Insert and delete data in a deque container

Function prototypes:

Operations at both ends:

• push_back(elem); //add data at the tail of the container
• push_front(elem); //insert data at the head of the container
• pop_back(); //delete the last data of the container
• pop_front(); //delete the first data of the container

Operations at a specified position:

• insert(pos,elem); //insert a copy of an elem element at position pos, return the position of the new data

• insert(pos,n,elem); //insert n elem data at position pos, no return value

• insert(pos,beg,end); //insert the data in the [beg,end) range at position pos, no return value

• clear(); //clear all data of the container

• erase(beg,end); //delete the data in the [beg,end) range, return the position of the next data

• erase(pos); //delete the data at position pos, return the position of the next data

Example:

#include <deque>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}
//两端操作
void test01()
{
	deque<int> d;
	//尾插
	d.push_back(10);
	d.push_back(20);
	//头插
	d.push_front(100);
	d.push_front(200);

	printDeque(d);

	//尾删
	d.pop_back();
	//头删
	d.pop_front();
	printDeque(d);
}

//插入
void test02()
{
	deque<int> d;
	d.push_back(10);
	d.push_back(20);
	d.push_front(100);
	d.push_front(200);
	printDeque(d);

	d.insert(d.begin(), 1000);
	printDeque(d);

	d.insert(d.begin(), 2,10000);
	printDeque(d);

	deque<int>d2;
	d2.push_back(1);
	d2.push_back(2);
	d2.push_back(3);

	d.insert(d.begin(), d2.begin(), d2.end());
	printDeque(d);

}

//删除
void test03()
{
	deque<int> d;
	d.push_back(10);
	d.push_back(20);
	d.push_front(100);
	d.push_front(200);
	printDeque(d);

	d.erase(d.begin());
	printDeque(d);

	d.erase(d.begin(), d.end());
	d.clear();
	printDeque(d);
}

int main() {

	//test01();

	//test02();

    test03();
    
	system("pause");

	return 0;
}

总结：

• 插入和删除提供的位置是迭代器！
• 尾插 — push_back
• 尾删 — pop_back
• 头插 — push_front
• 头删 — pop_front

deque 数据存取

功能描述：

• 对deque 中的数据的存取操作

函数原型：

• at(int idx); //返回索引idx所指的数据
• operator[]; //返回索引idx所指的数据
• front(); //返回容器中第一个数据元素
• back(); //返回容器中最后一个数据元素

示例：

Summary:

• The positions provided for insertion and deletion are iterators!
• Tail insertion — push_back
• Tail deletion — pop_back
• Head insertion — push_front
• Head deletion — pop_front

deque Data Access

Description:

• Access operations on data in a deque

Function prototypes:

• at(int idx); //return the data pointed by index idx
• operator[]; //return the data pointed by index idx
• front(); //return the first data element of the container
• back(); //return the last data element of the container

Example:

#include <deque>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}

//数据存取
void test01()
{

	deque<int> d;
	d.push_back(10);
	d.push_back(20);
	d.push_front(100);
	d.push_front(200);

	for (int i = 0; i < d.size(); i++) {
		cout << d[i] << " ";
	}
	cout << endl;


	for (int i = 0; i < d.size(); i++) {
		cout << d.at(i) << " ";
	}
	cout << endl;

	cout << "front:" << d.front() << endl;

	cout << "back:" << d.back() << endl;

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 除了用迭代器获取deque容器中元素，[ ]和at也可以
• front返回容器第一个元素
• back返回容器最后一个元素

deque 排序

功能描述：

• 利用算法实现对deque容器进行排序

算法：

• sort(iterator beg, iterator end) //对beg和end区间内元素进行排序

示例：

Summary:

• Besides using iterators to get elements in a deque container, [ ] and at also work
• front returns the first element of the container
• back returns the last element of the container

deque Sorting

Description:

• Use algorithms to sort a deque container

Algorithm:

• sort(iterator beg, iterator end) //sort the elements in the beg and end range

Example:

#include <deque>
#include <algorithm>

void printDeque(const deque<int>& d) 
{
	for (deque<int>::const_iterator it = d.begin(); it != d.end(); it++) {
		cout << *it << " ";

	}
	cout << endl;
}

void test01()
{

	deque<int> d;
	d.push_back(10);
	d.push_back(20);
	d.push_front(100);
	d.push_front(200);

	printDeque(d);
	sort(d.begin(), d.end());
	printDeque(d);

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：sort算法非常实用，使用时包含头文件 algorithm即可

案例-评委打分

案例描述

有5名选手：选手ABCDE，10个评委分别对每一名选手打分，去除最高分，去除评委中最低分，取平均分。

实现步骤

1. 创建五名选手，放到vector中
2. 遍历vector容器，取出来每一个选手，执行for循环，可以把10个评分打分存到deque容器中
3. sort算法对deque容器中分数排序，去除最高和最低分
4. deque容器遍历一遍，累加总分
5. 获取平均分

示例代码：

Summary: the sort algorithm is very practical; just include the header file algorithm when using it

Case: Judge Scoring

Case Description

There are 5 contestants: contestants ABCDE, and 10 judges each score every contestant. Remove the highest score and the lowest score among the judges, then take the average.

Implementation Steps

1. Create five contestants and put them into a vector
2. Traverse the vector container, take out each contestant, and run a for loop to store the 10 scores into a deque container
3. Use the sort algorithm to sort the scores in the deque container, removing the highest and lowest scores
4. Traverse the deque container once and accumulate the total score
5. Get the average score

Example code:

//选手类
class Person
{
public:
	Person(string name, int score)
	{
		this->m_Name = name;
		this->m_Score = score;
	}

	string m_Name; //姓名
	int m_Score;  //平均分
};

void createPerson(vector<Person>&v)
{
	string nameSeed = "ABCDE";
	for (int i = 0; i < 5; i++)
	{
		string name = "选手";
		name += nameSeed[i];

		int score = 0;

		Person p(name, score);

		//将创建的person对象 放入到容器中
		v.push_back(p);
	}
}

//打分
void setScore(vector<Person>&v)
{
	for (vector<Person>::iterator it = v.begin(); it != v.end(); it++)
	{
		//将评委的分数 放入到deque容器中
		deque<int>d;
		for (int i = 0; i < 10; i++)
		{
			int score = rand() % 41 + 60;  // 60 ~ 100
			d.push_back(score);
		}

		//cout << "选手： " << it->m_Name << " 打分： " << endl;
		//for (deque<int>::iterator dit = d.begin(); dit != d.end(); dit++)
		//{
		//	cout << *dit << " ";
		//}
		//cout << endl;

		//排序
		sort(d.begin(), d.end());

		//去除最高和最低分
		d.pop_back();
		d.pop_front();

		//取平均分
		int sum = 0;
		for (deque<int>::iterator dit = d.begin(); dit != d.end(); dit++)
		{
			sum += *dit; //累加每个评委的分数
		}

		int avg = sum / d.size();

		//将平均分 赋值给选手身上
		it->m_Score = avg;
	}

}

void showScore(vector<Person>&v)
{
	for (vector<Person>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << "姓名： " << it->m_Name << " 平均分： " << it->m_Score << endl;
	}
}

int main() {

	//随机数种子
	srand((unsigned int)time(NULL));

	//1、创建5名选手
	vector<Person>v;  //存放选手容器
	createPerson(v);

	//测试
	//for (vector<Person>::iterator it = v.begin(); it != v.end(); it++)
	//{
	//	cout << "姓名： " << (*it).m_Name << " 分数： " << (*it).m_Score << endl;
	//}

	//2、给5名选手打分
	setScore(v);

	//3、显示最后得分
	showScore(v);

	system("pause");

	return 0;
}

总结： 选取不同的容器操作数据，可以提升代码的效率

stack容器

stack 基本概念

概念：stack是一种先进后出(First In Last Out,FILO)的数据结构，它只有一个出口

栈中只有顶端的元素才可以被外界使用，因此栈不允许有遍历行为

栈中进入数据称为 — 入栈 push

栈中弹出数据称为 — 出栈 pop

生活中的栈：

stack 常用接口

功能描述：栈容器常用的对外接口

构造函数：

• stack<T> stk; //stack采用模板类实现， stack对象的默认构造形式
• stack(const stack &stk); //拷贝构造函数

赋值操作：

• stack& operator=(const stack &stk); //重载等号操作符

数据存取：

• push(elem); //向栈顶添加元素
• pop(); //从栈顶移除第一个元素
• top(); //返回栈顶元素

大小操作：

• empty(); //判断堆栈是否为空
• size(); //返回栈的大小

示例：

Summary: choosing different containers to operate on data can improve code efficiency

stack Container

stack Basic Concepts

Concept: stack is a first in last out (First In Last Out, FILO) data structure with only one exit

Only the element at the top of the stack can be used by the outside world, so the stack does not allow traversal behavior

Data entering the stack is called — push push

Data popping out of the stack is called — pop pop

Stacks in daily life:

stack Common Interfaces

Description: the common external interfaces of the stack container

Constructors:

• stack<T> stk; //implemented with a template class, the default construction form of a stack object
• stack(const stack &stk); //copy constructor

Assignment operations:

• stack& operator=(const stack &stk); //overload the assignment operator

Data access:

• push(elem); //add an element to the top of the stack
• pop(); //remove the first element from the top of the stack
• top(); //return the top element of the stack

Size operations:

• empty(); //check whether the stack is empty
• size(); //return the size of the stack

Example:

#include <stack>

//栈容器常用接口
void test01()
{
	//创建栈容器 栈容器必须符合先进后出
	stack<int> s;

	//向栈中添加元素，叫做 压栈 入栈
	s.push(10);
	s.push(20);
	s.push(30);

	while (!s.empty()) {
		//输出栈顶元素
		cout << "栈顶元素为： " << s.top() << endl;
		//弹出栈顶元素
		s.pop();
	}
	cout << "栈的大小为：" << s.size() << endl;

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 入栈 — push
• 出栈 — pop
• 返回栈顶 — top
• 判断栈是否为空 — empty
• 返回栈大小 — size

queue 容器

queue 基本概念

概念：Queue是一种先进先出(First In First Out,FIFO)的数据结构，它有两个出口

队列容器允许从一端新增元素，从另一端移除元素

队列中只有队头和队尾才可以被外界使用，因此队列不允许有遍历行为

队列中进数据称为 — 入队 push

队列中出数据称为 — 出队 pop

生活中的队列：

queue 常用接口

功能描述：栈容器常用的对外接口

构造函数：

• queue<T> que; //queue采用模板类实现，queue对象的默认构造形式
• queue(const queue &que); //拷贝构造函数

赋值操作：

• queue& operator=(const queue &que); //重载等号操作符

数据存取：

• push(elem); //往队尾添加元素
• pop(); //从队头移除第一个元素
• back(); //返回最后一个元素
• front(); //返回第一个元素

大小操作：

• empty(); //判断堆栈是否为空
• size(); //返回栈的大小

示例：

Summary:

• Push — push
• Pop — pop
• Return the top of the stack — top
• Check whether the stack is empty — empty
• Return the stack size — size

queue Container

queue Basic Concepts

Concept: Queue is a first in first out (First In First Out, FIFO) data structure with two exits

The queue container allows adding elements at one end and removing elements at the other end

Only the head and tail of the queue can be used by the outside world, so the queue does not allow traversal behavior

Data entering the queue is called — enqueue push

Data leaving the queue is called — dequeue pop

Queues in daily life:

queue Common Interfaces

Description: the common external interfaces of the queue container

Constructors:

• queue<T> que; //implemented with a template class, the default construction form of a queue object
• queue(const queue &que); //copy constructor

Assignment operations:

• queue& operator=(const queue &que); //overload the assignment operator

Data access:

• push(elem); //add an element to the tail of the queue
• pop(); //remove the first element from the head of the queue
• back(); //return the last element
• front(); //return the first element

Size operations:

• empty(); //check whether the queue is empty
• size(); //return the size of the queue

Example:

#include <queue>
#include <string>
class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	string m_Name;
	int m_Age;
};

void test01() {

	//创建队列
	queue<Person> q;

	//准备数据
	Person p1("唐僧", 30);
	Person p2("孙悟空", 1000);
	Person p3("猪八戒", 900);
	Person p4("沙僧", 800);

	//向队列中添加元素  入队操作
	q.push(p1);
	q.push(p2);
	q.push(p3);
	q.push(p4);

	//队列不提供迭代器，更不支持随机访问	
	while (!q.empty()) {
		//输出队头元素
		cout << "队头元素-- 姓名： " << q.front().m_Name 
              << " 年龄： "<< q.front().m_Age << endl;
        
		cout << "队尾元素-- 姓名： " << q.back().m_Name  
              << " 年龄： " << q.back().m_Age << endl;
        
		cout << endl;
		//弹出队头元素
		q.pop();
	}

	cout << "队列大小为：" << q.size() << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 入队 — push
• 出队 — pop
• 返回队头元素 — front
• 返回队尾元素 — back
• 判断队是否为空 — empty
• 返回队列大小 — size

list容器

list基本概念

**功能：**将数据进行链式存储

链表（list）是一种物理存储单元上非连续的存储结构，数据元素的逻辑顺序是通过链表中的指针链接实现的

链表的组成：链表由一系列结点组成

结点的组成：一个是存储数据元素的数据域，另一个是存储下一个结点地址的指针域

STL中的链表是一个双向循环链表

由于链表的存储方式并不是连续的内存空间，因此链表list中的迭代器只支持前移和后移，属于双向迭代器

list的优点：

• 采用动态存储分配，不会造成内存浪费和溢出
• 链表执行插入和删除操作十分方便，修改指针即可，不需要移动大量元素

list的缺点：

• 链表灵活，但是空间(指针域) 和 时间（遍历）额外耗费较大

List有一个重要的性质，插入操作和删除操作都不会造成原有list迭代器的失效，这在vector是不成立的。

总结：STL中List和vector是两个最常被使用的容器，各有优缺点

list构造函数

功能描述：

• 创建list容器

函数原型：

• list<T> lst; //list采用采用模板类实现,对象的默认构造形式：
• list(beg,end); //构造函数将[beg, end)区间中的元素拷贝给本身。
• list(n,elem); //构造函数将n个elem拷贝给本身。
• list(const list &lst); //拷贝构造函数。

示例：

Summary:

• Enqueue — push
• Dequeue — pop
• Return the head element — front
• Return the tail element — back
• Check whether the queue is empty — empty
• Return the queue size — size

list Container

list Basic Concepts

Features: store data in a chained manner

A linked list (list) is a storage structure that is non-contiguous in physical storage units; the logical order of data elements is implemented through pointers in the linked list

Composition of a linked list: a linked list consists of a series of nodes

Composition of a node: one is the data field that stores the data element, and the other is the pointer field that stores the address of the next node

The linked list in STL is a doubly circular linked list

Since the storage of a linked list is not contiguous memory space, the iterators of a list only support moving forward and backward, making them bidirectional iterators

Advantages of list:

• Uses dynamic storage allocation, so it does not waste memory or overflow
• Insertion and deletion operations on a linked list are very convenient; just modify the pointers, no need to move a large number of elements

Disadvantages of list:

• A linked list is flexible, but it costs extra space (pointer fields) and time (traversal)

An important property of List: insertion and deletion operations do not invalidate the existing iterators of the list, which is not true for vector.

Summary: List and vector are the two most commonly used containers in STL, each with its own advantages and disadvantages

list Constructors

Description:

• Create a list container

Function prototypes:

• list<T> lst; //implemented with a template class, the default construction form of the object
• list(beg,end); //the constructor copies the elements in the [beg, end) range to itself
• list(n,elem); //the constructor copies n elems to itself
• list(const list &lst); //copy constructor

Example:

#include <list>

void printList(const list<int>& L) {

	for (list<int>::const_iterator it = L.begin(); it != L.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

void test01()
{
	list<int>L1;
	L1.push_back(10);
	L1.push_back(20);
	L1.push_back(30);
	L1.push_back(40);

	printList(L1);

	list<int>L2(L1.begin(),L1.end());
	printList(L2);

	list<int>L3(L2);
	printList(L3);

	list<int>L4(10, 1000);
	printList(L4);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：list构造方式同其他几个STL常用容器，熟练掌握即可

list 赋值和交换

功能描述：

• 给list容器进行赋值，以及交换list容器

函数原型：

• assign(beg, end); //将[beg, end)区间中的数据拷贝赋值给本身。
• assign(n, elem); //将n个elem拷贝赋值给本身。
• list& operator=(const list &lst); //重载等号操作符
• swap(lst); //将lst与本身的元素互换。

示例：

Summary: the construction methods of list are the same as other common STL containers; master them skillfully

list Assignment and Swap

Description:

• Assign values to a list container and swap list containers

Function prototypes:

• assign(beg, end); //copy and assign the data in the [beg, end) range to itself
• assign(n, elem); //copy and assign n elems to itself
• list& operator=(const list &lst); //overload the assignment operator
• swap(lst); //swap the elements of lst with its own elements

Example:

#include <list>

void printList(const list<int>& L) {

	for (list<int>::const_iterator it = L.begin(); it != L.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

//赋值和交换
void test01()
{
	list<int>L1;
	L1.push_back(10);
	L1.push_back(20);
	L1.push_back(30);
	L1.push_back(40);
	printList(L1);

	//赋值
	list<int>L2;
	L2 = L1;
	printList(L2);

	list<int>L3;
	L3.assign(L2.begin(), L2.end());
	printList(L3);

	list<int>L4;
	L4.assign(10, 100);
	printList(L4);

}

//交换
void test02()
{

	list<int>L1;
	L1.push_back(10);
	L1.push_back(20);
	L1.push_back(30);
	L1.push_back(40);

	list<int>L2;
	L2.assign(10, 100);

	cout << "交换前： " << endl;
	printList(L1);
	printList(L2);

	cout << endl;

	L1.swap(L2);

	cout << "交换后： " << endl;
	printList(L1);
	printList(L2);

}

int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结：list赋值和交换操作能够灵活运用即可

list 大小操作

功能描述：

• 对list容器的大小进行操作

函数原型：

• size(); //返回容器中元素的个数

• empty(); //判断容器是否为空

• resize(num); //重新指定容器的长度为num，若容器变长，则以默认值填充新位置。

  ​ //如果容器变短，则末尾超出容器长度的元素被删除。

• resize(num, elem); //重新指定容器的长度为num，若容器变长，则以elem值填充新位置。如果容器变短，则末尾超出容器长度的元素被删除。

示例：

Summary: list assignment and swap operations can be used flexibly

list Size Operations

Description:

• Operations on the size of a list container

Function prototypes:

• size(); //return the number of elements in the container

• empty(); //check whether the container is empty

• resize(num); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with default values

  //if the container becomes shorter, the elements beyond the container length at the end are deleted

• resize(num, elem); //re-specify the length of the container as num; if the container becomes longer, fill the new positions with elem values. If the container becomes shorter, the elements beyond the container length at the end are deleted

Example:

#include <list>

void printList(const list<int>& L) {

	for (list<int>::const_iterator it = L.begin(); it != L.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

//大小操作
void test01()
{
	list<int>L1;
	L1.push_back(10);
	L1.push_back(20);
	L1.push_back(30);
	L1.push_back(40);

	if (L1.empty())
	{
		cout << "L1为空" << endl;
	}
	else
	{
		cout << "L1不为空" << endl;
		cout << "L1的大小为： " << L1.size() << endl;
	}

	//重新指定大小
	L1.resize(10);
	printList(L1);

	L1.resize(2);
	printList(L1);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 判断是否为空 — empty
• 返回元素个数 — size
• 重新指定个数 — resize

list 插入和删除

功能描述：

• 对list容器进行数据的插入和删除

函数原型：

• push_back(elem);//在容器尾部加入一个元素
• pop_back();//删除容器中最后一个元素
• push_front(elem);//在容器开头插入一个元素
• pop_front();//从容器开头移除第一个元素
• insert(pos,elem);//在pos位置插elem元素的拷贝，返回新数据的位置。
• insert(pos,n,elem);//在pos位置插入n个elem数据，无返回值。
• insert(pos,beg,end);//在pos位置插入[beg,end)区间的数据，无返回值。
• clear();//移除容器的所有数据
• erase(beg,end);//删除[beg,end)区间的数据，返回下一个数据的位置。
• erase(pos);//删除pos位置的数据，返回下一个数据的位置。
• remove(elem);//删除容器中所有与elem值匹配的元素。

示例：

Summary:

• Check whether it is empty — empty
• Return the number of elements — size
• Re-specify the count — resize

list Insert and Erase

Description:

• Insert and delete data in a list container

Function prototypes:

• push_back(elem);//add an element at the tail of the container
• pop_back();//delete the last element of the container
• push_front(elem);//insert an element at the head of the container
• pop_front();//remove the first element from the head of the container
• insert(pos,elem);//insert a copy of the elem element at position pos, return the position of the new data
• insert(pos,n,elem);//insert n elem data at position pos, no return value
• insert(pos,beg,end);//insert the data in the [beg,end) range at position pos, no return value
• clear();//remove all data of the container
• erase(beg,end);//delete the data in the [beg,end) range, return the position of the next data
• erase(pos);//delete the data at position pos, return the position of the next data
• remove(elem);//delete all elements matching the value of elem in the container

Example:

#include <list>

void printList(const list<int>& L) {

	for (list<int>::const_iterator it = L.begin(); it != L.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

//插入和删除
void test01()
{
	list<int> L;
	//尾插
	L.push_back(10);
	L.push_back(20);
	L.push_back(30);
	//头插
	L.push_front(100);
	L.push_front(200);
	L.push_front(300);

	printList(L);

	//尾删
	L.pop_back();
	printList(L);

	//头删
	L.pop_front();
	printList(L);

	//插入
	list<int>::iterator it = L.begin();
	L.insert(++it, 1000);
	printList(L);

	//删除
	it = L.begin();
	L.erase(++it);
	printList(L);

	//移除
	L.push_back(10000);
	L.push_back(10000);
	L.push_back(10000);
	printList(L);
	L.remove(10000);
	printList(L);
    
    //清空
	L.clear();
	printList(L);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 尾插 — push_back
• 尾删 — pop_back
• 头插 — push_front
• 头删 — pop_front
• 插入 — insert
• 删除 — erase
• 移除 — remove
• 清空 — clear

list 数据存取

功能描述：

• 对list容器中数据进行存取

函数原型：

• front(); //返回第一个元素。
• back(); //返回最后一个元素。

示例：

Summary:

• Tail insertion — push_back
• Tail deletion — pop_back
• Head insertion — push_front
• Head deletion — pop_front
• Insertion — insert
• Deletion — erase
• Removal — remove
• Clear — clear

list Data Access

Description:

• Access data in a list container

Function prototypes:

• front(); //return the first element
• back(); //return the last element

Example:

#include <list>

//数据存取
void test01()
{
	list<int>L1;
	L1.push_back(10);
	L1.push_back(20);
	L1.push_back(30);
	L1.push_back(40);

	
	//cout << L1.at(0) << endl;//错误 不支持at访问数据
	//cout << L1[0] << endl; //错误  不支持[]方式访问数据
	cout << "第一个元素为： " << L1.front() << endl;
	cout << "最后一个元素为： " << L1.back() << endl;

	//list容器的迭代器是双向迭代器，不支持随机访问
	list<int>::iterator it = L1.begin();
	//it = it + 1;//错误，不可以跳跃访问，即使是+1
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• list容器中不可以通过[]或者at方式访问数据
• 返回第一个元素 — front
• 返回最后一个元素 — back

list 反转和排序

功能描述：

• 将容器中的元素反转，以及将容器中的数据进行排序

函数原型：

• reverse(); //反转链表
• sort(); //链表排序

示例：

Summary:

• Data in a list container cannot be accessed with [] or at
• Return the first element — front
• Return the last element — back

list Reverse and Sort

Description:

• Reverse the elements in the container and sort the data in the container

Function prototypes:

• reverse(); //reverse the linked list
• sort(); //sort the linked list

Example:

void printList(const list<int>& L) {

	for (list<int>::const_iterator it = L.begin(); it != L.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

bool myCompare(int val1 , int val2)
{
	return val1 > val2;
}

//反转和排序
void test01()
{
	list<int> L;
	L.push_back(90);
	L.push_back(30);
	L.push_back(20);
	L.push_back(70);
	printList(L);

	//反转容器的元素
	L.reverse();
	printList(L);

	//排序
	L.sort(); //默认的排序规则 从小到大
	printList(L);

	L.sort(myCompare); //指定规则，从大到小
	printList(L);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 反转 — reverse
• 排序 — sort （成员函数）

排序案例

案例描述：将Person自定义数据类型进行排序，Person中属性有姓名、年龄、身高

排序规则：按照年龄进行升序，如果年龄相同按照身高进行降序

示例：

Summary:

• Reverse — reverse
• Sort — sort (member function)

Sorting Case

Case description: sort a custom data type Person; Person has the attributes name, age, and height

Sorting rule: ascending by age; if ages are equal, descending by height

Example:

#include <list>
#include <string>
class Person {
public:
	Person(string name, int age , int height) {
		m_Name = name;
		m_Age = age;
		m_Height = height;
	}

public:
	string m_Name;  //姓名
	int m_Age;      //年龄
	int m_Height;   //身高
};


bool ComparePerson(Person& p1, Person& p2) {

	if (p1.m_Age == p2.m_Age) {
		return p1.m_Height  > p2.m_Height;
	}
	else
	{
		return  p1.m_Age < p2.m_Age;
	}

}

void test01() {

	list<Person> L;

	Person p1("刘备", 35 , 175);
	Person p2("曹操", 45 , 180);
	Person p3("孙权", 40 , 170);
	Person p4("赵云", 25 , 190);
	Person p5("张飞", 35 , 160);
	Person p6("关羽", 35 , 200);

	L.push_back(p1);
	L.push_back(p2);
	L.push_back(p3);
	L.push_back(p4);
	L.push_back(p5);
	L.push_back(p6);

	for (list<Person>::iterator it = L.begin(); it != L.end(); it++) {
		cout << "姓名： " << it->m_Name << " 年龄： " << it->m_Age 
              << " 身高： " << it->m_Height << endl;
	}

	cout << "---------------------------------" << endl;
	L.sort(ComparePerson); //排序

	for (list<Person>::iterator it = L.begin(); it != L.end(); it++) {
		cout << "姓名： " << it->m_Name << " 年龄： " << it->m_Age 
              << " 身高： " << it->m_Height << endl;
	}
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 对于自定义数据类型，必须要指定排序规则，否则编译器不知道如何进行排序

• 高级排序只是在排序规则上再进行一次逻辑规则制定，并不复杂

set/ multiset 容器

set基本概念

简介：

• 所有元素都会在插入时自动被排序

本质：

• set/multiset属于关联式容器，底层结构是用二叉树实现。

set和multiset区别：

• set不允许容器中有重复的元素
• multiset允许容器中有重复的元素

set构造和赋值

功能描述：创建set容器以及赋值

构造：

• set<T> st; //默认构造函数：
• set(const set &st); //拷贝构造函数

赋值：

• set& operator=(const set &st); //重载等号操作符

示例：

Summary:

• For custom data types, a sorting rule must be specified, otherwise the compiler does not know how to sort

• Advanced sorting is just adding another logical rule on top of the sorting rule; it is not complicated

set/multiset Containers

set Basic Concepts

Introduction:

• All elements are automatically sorted when inserted

Essence:

• set/multiset are associative containers, implemented with a binary tree at the bottom level

Differences between set and multiset:

• set does not allow duplicate elements in the container
• multiset allows duplicate elements in the container

set Construction and Assignment

Description: create a set container and assign values

Construction:

• set<T> st; //default constructor
• set(const set &st); //copy constructor

Assignment:

• set& operator=(const set &st); //overload the assignment operator

Example:

#include <set>

void printSet(set<int> & s)
{
	for (set<int>::iterator it = s.begin(); it != s.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

//构造和赋值
void test01()
{
	set<int> s1;

	s1.insert(10);
	s1.insert(30);
	s1.insert(20);
	s1.insert(40);
	printSet(s1);

	//拷贝构造
	set<int>s2(s1);
	printSet(s2);

	//赋值
	set<int>s3;
	s3 = s2;
	printSet(s3);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• set容器插入数据时用insert
• set容器插入数据的数据会自动排序

set大小和交换

功能描述：

• 统计set容器大小以及交换set容器

函数原型：

• size(); //返回容器中元素的数目
• empty(); //判断容器是否为空
• swap(st); //交换两个集合容器

示例：

Summary:

• Use insert to insert data into a set container
• Data inserted into a set container is automatically sorted

set Size and Swap

Description:

• Count the size of a set container and swap set containers

Function prototypes:

• size(); //return the number of elements in the container
• empty(); //check whether the container is empty
• swap(st); //swap two set containers

Example:

#include <set>

void printSet(set<int> & s)
{
	for (set<int>::iterator it = s.begin(); it != s.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

//大小
void test01()
{

	set<int> s1;
	
	s1.insert(10);
	s1.insert(30);
	s1.insert(20);
	s1.insert(40);

	if (s1.empty())
	{
		cout << "s1为空" << endl;
	}
	else
	{
		cout << "s1不为空" << endl;
		cout << "s1的大小为： " << s1.size() << endl;
	}

}

//交换
void test02()
{
	set<int> s1;

	s1.insert(10);
	s1.insert(30);
	s1.insert(20);
	s1.insert(40);

	set<int> s2;

	s2.insert(100);
	s2.insert(300);
	s2.insert(200);
	s2.insert(400);

	cout << "交换前" << endl;
	printSet(s1);
	printSet(s2);
	cout << endl;

	cout << "交换后" << endl;
	s1.swap(s2);
	printSet(s1);
	printSet(s2);
}

int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结：

• 统计大小 — size
• 判断是否为空 — empty
• 交换容器 — swap

set插入和删除

功能描述：

• set容器进行插入数据和删除数据

函数原型：

• insert(elem); //在容器中插入元素。
• clear(); //清除所有元素
• erase(pos); //删除pos迭代器所指的元素，返回下一个元素的迭代器。
• erase(beg, end); //删除区间[beg,end)的所有元素 ，返回下一个元素的迭代器。
• erase(elem); //删除容器中值为elem的元素。

示例：

Summary:

• Count the size — size
• Check whether it is empty — empty
• Swap containers — swap

set Insert and Erase

Description:

• Insert and delete data in a set container

Function prototypes:

• insert(elem); //insert an element in the container
• clear(); //clear all elements
• erase(pos); //delete the element pointed by the pos iterator, return the iterator of the next element
• erase(beg, end); //delete all elements in the [beg,end) range, return the iterator of the next element
• erase(elem); //delete the element with value elem in the container

Example:

#include <set>

void printSet(set<int> & s)
{
	for (set<int>::iterator it = s.begin(); it != s.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

//插入和删除
void test01()
{
	set<int> s1;
	//插入
	s1.insert(10);
	s1.insert(30);
	s1.insert(20);
	s1.insert(40);
	printSet(s1);

	//删除
	s1.erase(s1.begin());
	printSet(s1);

	s1.erase(30);
	printSet(s1);

	//清空
	//s1.erase(s1.begin(), s1.end());
	s1.clear();
	printSet(s1);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 插入 — insert
• 删除 — erase
• 清空 — clear

set查找和统计

功能描述：

• 对set容器进行查找数据以及统计数据

函数原型：

• find(key); //查找key是否存在,若存在，返回该键的元素的迭代器；若不存在，返回set.end();
• count(key); //统计key的元素个数

示例：

Summary:

• Insertion — insert
• Deletion — erase
• Clear — clear

set Find and Count

Description:

• Search data and count data in a set container

Function prototypes:

• find(key); //check whether key exists; if it exists, return the iterator of the element with that key; if not, return set.end()
• count(key); //count the number of elements with key

Example:

#include <set>

//查找和统计
void test01()
{
	set<int> s1;
	//插入
	s1.insert(10);
	s1.insert(30);
	s1.insert(20);
	s1.insert(40);
	
	//查找
	set<int>::iterator pos = s1.find(30);

	if (pos != s1.end())
	{
		cout << "找到了元素 ： " << *pos << endl;
	}
	else
	{
		cout << "未找到元素" << endl;
	}

	//统计
	int num = s1.count(30);
	cout << "num = " << num << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 查找 — find （返回的是迭代器）
• 统计 — count （对于set，结果为0或者1）

set和multiset区别

学习目标：

• 掌握set和multiset的区别

区别：

• set不可以插入重复数据，而multiset可以
• set插入数据的同时会返回插入结果，表示插入是否成功
• multiset不会检测数据，因此可以插入重复数据

示例：

Summary:

• Find — find (returns an iterator)
• Count — count (for set, the result is 0 or 1)

Differences Between set and multiset

Learning objectives:

• Master the differences between set and multiset

Differences:

• set cannot insert duplicate data, while multiset can
• set returns the insertion result when inserting data, indicating whether the insertion succeeded
• multiset does not check data, so it can insert duplicate data

Example:

#include <set>

//set和multiset区别
void test01()
{
	set<int> s;
	pair<set<int>::iterator, bool>  ret = s.insert(10);
	if (ret.second) {
		cout << "第一次插入成功!" << endl;
	}
	else {
		cout << "第一次插入失败!" << endl;
	}

	ret = s.insert(10);
	if (ret.second) {
		cout << "第二次插入成功!" << endl;
	}
	else {
		cout << "第二次插入失败!" << endl;
	}
    
	//multiset
	multiset<int> ms;
	ms.insert(10);
	ms.insert(10);

	for (multiset<int>::iterator it = ms.begin(); it != ms.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 如果不允许插入重复数据可以利用set
• 如果需要插入重复数据利用multiset

pair对组创建

功能描述：

• 成对出现的数据，利用对组可以返回两个数据

两种创建方式：

• pair<type, type> p ( value1, value2 );
• pair<type, type> p = make_pair( value1, value2 );

示例：

Summary:

• If duplicate data is not allowed, use set
• If duplicate data needs to be inserted, use multiset

pair Creating Pairs

Description:

• For data that appears in pairs, a pair can be used to return two data values

Two ways to create:

• pair<type, type> p ( value1, value2 );
• pair<type, type> p = make_pair( value1, value2 );

Example:

#include <string>

//对组创建
void test01()
{
	pair<string, int> p(string("Tom"), 20);
	cout << "姓名： " <<  p.first << " 年龄： " << p.second << endl;

	pair<string, int> p2 = make_pair("Jerry", 10);
	cout << "姓名： " << p2.first << " 年龄： " << p2.second << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

两种方式都可以创建对组，记住一种即可

set容器排序

学习目标：

• set容器默认排序规则为从小到大，掌握如何改变排序规则

主要技术点：

• 利用仿函数，可以改变排序规则

示例一 set存放内置数据类型

Summary:

Both ways can create a pair; just remember one of them

set Container Sorting

Learning objectives:

• The default sorting rule of a set container is from small to large; master how to change the sorting rule

Key technical points:

• Functors can be used to change the sorting rule

Example 1 set storing built-in data types

#include <set>

class MyCompare 
{
public:
	bool operator()(int v1, int v2) {
		return v1 > v2;
	}
};
void test01() 
{    
	set<int> s1;
	s1.insert(10);
	s1.insert(40);
	s1.insert(20);
	s1.insert(30);
	s1.insert(50);

	//默认从小到大
	for (set<int>::iterator it = s1.begin(); it != s1.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;

	//指定排序规则
	set<int,MyCompare> s2;
	s2.insert(10);
	s2.insert(40);
	s2.insert(20);
	s2.insert(30);
	s2.insert(50);

	for (set<int, MyCompare>::iterator it = s2.begin(); it != s2.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：利用仿函数可以指定set容器的排序规则

示例二 set存放自定义数据类型

Summary: functors can be used to specify the sorting rule of a set container

Example 2 set storing custom data types

#include <set>
#include <string>

class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	string m_Name;
	int m_Age;

};
class comparePerson
{
public:
	bool operator()(const Person& p1, const Person &p2)
	{
		//按照年龄进行排序  降序
		return p1.m_Age > p2.m_Age;
	}
};

void test01()
{
	set<Person, comparePerson> s;

	Person p1("刘备", 23);
	Person p2("关羽", 27);
	Person p3("张飞", 25);
	Person p4("赵云", 21);

	s.insert(p1);
	s.insert(p2);
	s.insert(p3);
	s.insert(p4);

	for (set<Person, comparePerson>::iterator it = s.begin(); it != s.end(); it++)
	{
		cout << "姓名： " << it->m_Name << " 年龄： " << it->m_Age << endl;
	}
}
int main() {

	test01();

	system("pause");

	return 0;
}

总结：

对于自定义数据类型，set必须指定排序规则才可以插入数据

map/ multimap容器

map基本概念

简介：

• map中所有元素都是pair
• pair中第一个元素为key（键值），起到索引作用，第二个元素为value（实值）
• 所有元素都会根据元素的键值自动排序

本质：

• map/multimap属于关联式容器，底层结构是用二叉树实现。

优点：

• 可以根据key值快速找到value值

map和multimap区别：

• map不允许容器中有重复key值元素
• multimap允许容器中有重复key值元素

map构造和赋值

功能描述：

• 对map容器进行构造和赋值操作

函数原型：

构造：

• map<T1, T2> mp; //map默认构造函数:
• map(const map &mp); //拷贝构造函数

赋值：

• map& operator=(const map &mp); //重载等号操作符

示例：

Summary:

For custom data types, set must specify a sorting rule before data can be inserted

map/multimap Containers

map Basic Concepts

Introduction:

• All elements in a map are pairs
• The first element of a pair is the key (key value), which serves as an index; the second element is the value (actual value)
• All elements are automatically sorted by their key values

Essence:

• map/multimap are associative containers, implemented with a binary tree at the bottom level

Advantages:

• Values can be quickly found by key value

Differences between map and multimap:

• map does not allow elements with duplicate key values
• multimap allows elements with duplicate key values

map Construction and Assignment

Description:

• Construct and assign values to a map container

Function prototypes:

Construction:

• map<T1, T2> mp; //map default constructor
• map(const map &mp); //copy constructor

Assignment:

• map& operator=(const map &mp); //overload the assignment operator

Example:

#include <map>

void printMap(map<int,int>&m)
{
	for (map<int, int>::iterator it = m.begin(); it != m.end(); it++)
	{
		cout << "key = " << it->first << " value = " << it->second << endl;
	}
	cout << endl;
}

void test01()
{
	map<int,int>m; //默认构造
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));
	printMap(m);

	map<int, int>m2(m); //拷贝构造
	printMap(m2);

	map<int, int>m3;
	m3 = m2; //赋值
	printMap(m3);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：map中所有元素都是成对出现，插入数据时候要使用对组

map大小和交换

功能描述：

• 统计map容器大小以及交换map容器

函数原型：

• size(); //返回容器中元素的数目
• empty(); //判断容器是否为空
• swap(st); //交换两个集合容器

示例：

Summary: all elements in a map appear in pairs; use a pair when inserting data

map Size and Swap

Description:

• Count the size of a map container and swap map containers

Function prototypes:

• size(); //return the number of elements in the container
• empty(); //check whether the container is empty
• swap(st); //swap two set containers

Example:

#include <map>

void printMap(map<int,int>&m)
{
	for (map<int, int>::iterator it = m.begin(); it != m.end(); it++)
	{
		cout << "key = " << it->first << " value = " << it->second << endl;
	}
	cout << endl;
}

void test01()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));

	if (m.empty())
	{
		cout << "m为空" << endl;
	}
	else
	{
		cout << "m不为空" << endl;
		cout << "m的大小为： " << m.size() << endl;
	}
}


//交换
void test02()
{
	map<int, int>m;
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));

	map<int, int>m2;
	m2.insert(pair<int, int>(4, 100));
	m2.insert(pair<int, int>(5, 200));
	m2.insert(pair<int, int>(6, 300));

	cout << "交换前" << endl;
	printMap(m);
	printMap(m2);

	cout << "交换后" << endl;
	m.swap(m2);
	printMap(m);
	printMap(m2);
}

int main() {

	test01();

	test02();

	system("pause");

	return 0;
}

总结：

• 统计大小 — size
• 判断是否为空 — empty
• 交换容器 — swap

map插入和删除

功能描述：

• map容器进行插入数据和删除数据

函数原型：

• insert(elem); //在容器中插入元素。
• clear(); //清除所有元素
• erase(pos); //删除pos迭代器所指的元素，返回下一个元素的迭代器。
• erase(beg, end); //删除区间[beg,end)的所有元素 ，返回下一个元素的迭代器。
• erase(key); //删除容器中值为key的元素。

示例：

Summary:

• Count the size — size
• Check whether it is empty — empty
• Swap containers — swap

map Insert and Erase

Description:

• Insert and delete data in a map container

Function prototypes:

• insert(elem); //insert an element in the container
• clear(); //clear all elements
• erase(pos); //delete the element pointed by the pos iterator, return the iterator of the next element
• erase(beg, end); //delete all elements in the [beg,end) range, return the iterator of the next element
• erase(key); //delete the element with value key in the container

Example:

#include <map>

void printMap(map<int,int>&m)
{
	for (map<int, int>::iterator it = m.begin(); it != m.end(); it++)
	{
		cout << "key = " << it->first << " value = " << it->second << endl;
	}
	cout << endl;
}

void test01()
{
	//插入
	map<int, int> m;
	//第一种插入方式
	m.insert(pair<int, int>(1, 10));
	//第二种插入方式
	m.insert(make_pair(2, 20));
	//第三种插入方式
	m.insert(map<int, int>::value_type(3, 30));
	//第四种插入方式
	m[4] = 40; 
	printMap(m);

	//删除
	m.erase(m.begin());
	printMap(m);

	m.erase(3);
	printMap(m);

	//清空
	m.erase(m.begin(),m.end());
	m.clear();
	printMap(m);
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• map插入方式很多，记住其一即可

• 插入 — insert
• 删除 — erase
• 清空 — clear

map查找和统计

功能描述：

• 对map容器进行查找数据以及统计数据

函数原型：

• find(key); //查找key是否存在,若存在，返回该键的元素的迭代器；若不存在，返回set.end();
• count(key); //统计key的元素个数

示例：

Summary:

• There are many ways to insert into a map; just remember one of them

• Insertion — insert
• Deletion — erase
• Clear — clear

map Find and Count

Description:

• Search data and count data in a map container

Function prototypes:

• find(key); //check whether key exists; if it exists, return the iterator of the element with that key; if not, return set.end()
• count(key); //count the number of elements with key

Example:

#include <map>

//查找和统计
void test01()
{
	map<int, int>m; 
	m.insert(pair<int, int>(1, 10));
	m.insert(pair<int, int>(2, 20));
	m.insert(pair<int, int>(3, 30));

	//查找
	map<int, int>::iterator pos = m.find(3);

	if (pos != m.end())
	{
		cout << "找到了元素 key = " << (*pos).first << " value = " << (*pos).second << endl;
	}
	else
	{
		cout << "未找到元素" << endl;
	}

	//统计
	int num = m.count(3);
	cout << "num = " << num << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 查找 — find （返回的是迭代器）
• 统计 — count （对于map，结果为0或者1）

map容器排序

学习目标：

• map容器默认排序规则为 按照key值进行 从小到大排序，掌握如何改变排序规则

主要技术点:

• 利用仿函数，可以改变排序规则

示例：

Summary:

• Find — find (returns an iterator)
• Count — count (for map, the result is 0 or 1)

map Container Sorting

Learning objectives:

• The default sorting rule of a map container is ascending by key value; master how to change the sorting rule

Key technical points:

• Functors can be used to change the sorting rule

Example:

#include <map>

class MyCompare {
public:
	bool operator()(int v1, int v2) {
		return v1 > v2;
	}
};

void test01() 
{
	//默认从小到大排序
	//利用仿函数实现从大到小排序
	map<int, int, MyCompare> m;

	m.insert(make_pair(1, 10));
	m.insert(make_pair(2, 20));
	m.insert(make_pair(3, 30));
	m.insert(make_pair(4, 40));
	m.insert(make_pair(5, 50));

	for (map<int, int, MyCompare>::iterator it = m.begin(); it != m.end(); it++) {
		cout << "key:" << it->first << " value:" << it->second << endl;
	}
}
int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 利用仿函数可以指定map容器的排序规则
• 对于自定义数据类型，map必须要指定排序规则,同set容器

案例-员工分组

案例描述

• 公司今天招聘了10个员工（ABCDEFGHIJ），10名员工进入公司之后，需要指派员工在那个部门工作
• 员工信息有: 姓名 工资组成；部门分为：策划、美术、研发
• 随机给10名员工分配部门和工资
• 通过multimap进行信息的插入 key(部门编号) value(员工)
• 分部门显示员工信息

实现步骤

1. 创建10名员工，放到vector中
2. 遍历vector容器，取出每个员工，进行随机分组
3. 分组后，将员工部门编号作为key，具体员工作为value，放入到multimap容器中
4. 分部门显示员工信息

案例代码：

Summary:

• Functors can be used to specify the sorting rule of a map container
• For custom data types, map must specify a sorting rule, same as set containers

Case: Employee Grouping

Case Description

• The company hired 10 employees (ABCDEFGHIJ) today; after entering the company, each employee needs to be assigned to a department
• Employee information includes: name and salary; departments: planning, art, R&D
• Randomly assign departments and salaries to the 10 employees
• Use multimap to insert information key (department number) value (employee)
• Display employee information by department

Implementation Steps

1. Create 10 employees and put them into a vector
2. Traverse the vector container, take out each employee, and group them randomly
3. After grouping, use the department number as the key and the specific employee as the value, and put them into a multimap container
4. Display employee information by department

Case code:

#include<iostream>
using namespace std;
#include <vector>
#include <string>
#include <map>
#include <ctime>

/*
- 公司今天招聘了10个员工（ABCDEFGHIJ），10名员工进入公司之后，需要指派员工在那个部门工作
- 员工信息有: 姓名  工资组成；部门分为：策划、美术、研发
- 随机给10名员工分配部门和工资
- 通过multimap进行信息的插入  key(部门编号) value(员工)
- 分部门显示员工信息
*/

#define CEHUA  0
#define MEISHU 1
#define YANFA  2

class Worker
{
public:
	string m_Name;
	int m_Salary;
};

void createWorker(vector<Worker>&v)
{
	string nameSeed = "ABCDEFGHIJ";
	for (int i = 0; i < 10; i++)
	{
		Worker worker;
		worker.m_Name = "员工";
		worker.m_Name += nameSeed[i];

		worker.m_Salary = rand() % 10000 + 10000; // 10000 ~ 19999
		//将员工放入到容器中
		v.push_back(worker);
	}
}

//员工分组
void setGroup(vector<Worker>&v,multimap<int,Worker>&m)
{
	for (vector<Worker>::iterator it = v.begin(); it != v.end(); it++)
	{
		//产生随机部门编号
		int deptId = rand() % 3; // 0 1 2 

		//将员工插入到分组中
		//key部门编号，value具体员工
		m.insert(make_pair(deptId, *it));
	}
}

void showWorkerByGourp(multimap<int,Worker>&m)
{
	// 0  A  B  C   1  D  E   2  F G ...
	cout << "策划部门：" << endl;

	multimap<int,Worker>::iterator pos = m.find(CEHUA);
	int count = m.count(CEHUA); // 统计具体人数
	int index = 0;
	for (; pos != m.end() && index < count; pos++ , index++)
	{
		cout << "姓名： " << pos->second.m_Name << " 工资： " << pos->second.m_Salary << endl;
	}

	cout << "----------------------" << endl;
	cout << "美术部门： " << endl;
	pos = m.find(MEISHU);
	count = m.count(MEISHU); // 统计具体人数
	index = 0;
	for (; pos != m.end() && index < count; pos++, index++)
	{
		cout << "姓名： " << pos->second.m_Name << " 工资： " << pos->second.m_Salary << endl;
	}

	cout << "----------------------" << endl;
	cout << "研发部门： " << endl;
	pos = m.find(YANFA);
	count = m.count(YANFA); // 统计具体人数
	index = 0;
	for (; pos != m.end() && index < count; pos++, index++)
	{
		cout << "姓名： " << pos->second.m_Name << " 工资： " << pos->second.m_Salary << endl;
	}

}

int main() {

	srand((unsigned int)time(NULL));

	//1、创建员工
	vector<Worker>vWorker;
	createWorker(vWorker);

	//2、员工分组
	multimap<int, Worker>mWorker;
	setGroup(vWorker, mWorker);


	//3、分组显示员工
	showWorkerByGourp(mWorker);

	////测试
	//for (vector<Worker>::iterator it = vWorker.begin(); it != vWorker.end(); it++)
	//{
	//	cout << "姓名： " << it->m_Name << " 工资： " << it->m_Salary << endl;
	//}

	system("pause");

	return 0;
}

总结：

• 当数据以键值对形式存在，可以考虑用map 或 multimap

STL- 函数对象

函数对象

函数对象概念

概念：

• 重载函数调用操作符的类，其对象常称为函数对象
• 函数对象使用重载的()时，行为类似函数调用，也叫仿函数

本质：

函数对象(仿函数)是一个类，不是一个函数

函数对象使用

特点：

• 函数对象在使用时，可以像普通函数那样调用, 可以有参数，可以有返回值
• 函数对象超出普通函数的概念，函数对象可以有自己的状态
• 函数对象可以作为参数传递

示例:

Summary:

• When data exists in the form of key-value pairs, consider using map or multimap

STL - Function Objects

Function Objects

The Concept of Function Objects

Concept:

• A class that overloads the function call operator; its objects are often called function objects
• When a function object uses the overloaded (), it behaves like a function call, and is also called a functor

Essence:

A function object (functor) is a class, not a function

Using Function Objects

Features:

• Function objects can be called like ordinary functions when used, with parameters and return values
• Function objects go beyond the concept of ordinary functions; they can have their own state
• Function objects can be passed as parameters

Example:

#include <string>

//1、函数对象在使用时，可以像普通函数那样调用, 可以有参数，可以有返回值
class MyAdd
{
public :
	int operator()(int v1,int v2)
	{
		return v1 + v2;
	}
};

void test01()
{
	MyAdd myAdd;
	cout << myAdd(10, 10) << endl;
}

//2、函数对象可以有自己的状态
class MyPrint
{
public:
	MyPrint()
	{
		count = 0;
	}
	void operator()(string test)
	{
		cout << test << endl;
		count++; //统计使用次数
	}

	int count; //内部自己的状态
};
void test02()
{
	MyPrint myPrint;
	myPrint("hello world");
	myPrint("hello world");
	myPrint("hello world");
	cout << "myPrint调用次数为： " << myPrint.count << endl;
}

//3、函数对象可以作为参数传递
void doPrint(MyPrint &mp , string test)
{
	mp(test);
}

void test03()
{
	MyPrint myPrint;
	doPrint(myPrint, "Hello C++");
}

int main() {

	//test01();
	//test02();
	test03();

	system("pause");

	return 0;
}

总结：

• 仿函数写法非常灵活，可以作为参数进行传递。

谓词

谓词概念

概念：

• 返回bool类型的仿函数称为谓词
• 如果operator()接受一个参数，那么叫做一元谓词
• 如果operator()接受两个参数，那么叫做二元谓词

一元谓词

示例：

Summary:

• Functors are very flexible to write and can be passed as parameters.

Predicates

The Concept of Predicates

Concept:

• Functors that return a bool type are called predicates
• If operator() accepts one parameter, it is called a unary predicate
• If operator() accepts two parameters, it is called a binary predicate

Unary Predicates

Example:

#include <vector>
#include <algorithm>

//1.一元谓词
struct GreaterFive{
	bool operator()(int val) {
		return val > 5;
	}
};

void test01() {

	vector<int> v;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
	if (it == v.end()) {
		cout << "没找到!" << endl;
	}
	else {
		cout << "找到:" << *it << endl;
	}

}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：参数只有一个的谓词，称为一元谓词

二元谓词

示例：

Summary: a predicate with only one parameter is called a unary predicate

Binary Predicates

Example:

#include <vector>
#include <algorithm>
//二元谓词
class MyCompare
{
public:
	bool operator()(int num1, int num2)
	{
		return num1 > num2;
	}
};

void test01()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(40);
	v.push_back(20);
	v.push_back(30);
	v.push_back(50);

	//默认从小到大
	sort(v.begin(), v.end());
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
	cout << "----------------------------" << endl;

	//使用函数对象改变算法策略，排序从大到小
	sort(v.begin(), v.end(), MyCompare());
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：参数只有两个的谓词，称为二元谓词

内建函数对象

内建函数对象意义

概念：

• STL内建了一些函数对象

分类:

• 算术仿函数

• 关系仿函数

• 逻辑仿函数

用法：

• 这些仿函数所产生的对象，用法和一般函数完全相同
• 使用内建函数对象，需要引入头文件 #include<functional>

算术仿函数

功能描述：

• 实现四则运算
• 其中negate是一元运算，其他都是二元运算

仿函数原型：

• template<class T> T plus<T> //加法仿函数
• template<class T> T minus<T> //减法仿函数
• template<class T> T multiplies<T> //乘法仿函数
• template<class T> T divides<T> //除法仿函数
• template<class T> T modulus<T> //取模仿函数
• template<class T> T negate<T> //取反仿函数

示例：

Summary: a predicate with only two parameters is called a binary predicate

Built-in Function Objects

The Significance of Built-in Function Objects

Concept:

• STL has some built-in function objects

Categories:

• Arithmetic functors

• Relational functors

• Logical functors

Usage:

• The objects produced by these functors are used exactly like ordinary functions
• To use built-in function objects, include the header file #include<functional>

Arithmetic Functors

Description:

• Implement the four basic arithmetic operations
• Among them, negate is a unary operation, and the others are binary operations

Functor prototypes:

• template<class T> T plus<T> //addition functor
• template<class T> T minus<T> //subtraction functor
• template<class T> T multiplies<T> //multiplication functor
• template<class T> T divides<T> //division functor
• template<class T> T modulus<T> //modulo functor
• template<class T> T negate<T> //negation functor

Example:

#include <functional>
//negate
void test01()
{
	negate<int> n;
	cout << n(50) << endl;
}

//plus
void test02()
{
	plus<int> p;
	cout << p(10, 20) << endl;
}

int main() {

	test01();
	test02();

	system("pause");

	return 0;
}

总结：使用内建函数对象时，需要引入头文件 #include <functional>

关系仿函数

功能描述：

• 实现关系对比

仿函数原型：

• template<class T> bool equal_to<T> //等于
• template<class T> bool not_equal_to<T> //不等于
• template<class T> bool greater<T> //大于
• template<class T> bool greater_equal<T> //大于等于
• template<class T> bool less<T> //小于
• template<class T> bool less_equal<T> //小于等于

示例：

Summary: when using built-in function objects, include the header file #include <functional>

Relational Functors

Description:

• Implement relational comparisons

Functor prototypes:

• template<class T> bool equal_to<T> //equal to
• template<class T> bool not_equal_to<T> //not equal to
• template<class T> bool greater<T> //greater than
• template<class T> bool greater_equal<T> //greater than or equal to
• template<class T> bool less<T> //less than
• template<class T> bool less_equal<T> //less than or equal to

Example:

#include <functional>
#include <vector>
#include <algorithm>

class MyCompare
{
public:
	bool operator()(int v1,int v2)
	{
		return v1 > v2;
	}
};
void test01()
{
	vector<int> v;

	v.push_back(10);
	v.push_back(30);
	v.push_back(50);
	v.push_back(40);
	v.push_back(20);

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;

	//自己实现仿函数
	//sort(v.begin(), v.end(), MyCompare());
	//STL内建仿函数  大于仿函数
	sort(v.begin(), v.end(), greater<int>());

	for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
		cout << *it << " ";
	}
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：关系仿函数中最常用的就是greater<>大于

逻辑仿函数

功能描述：

• 实现逻辑运算

函数原型：

• template<class T> bool logical_and<T> //逻辑与
• template<class T> bool logical_or<T> //逻辑或
• template<class T> bool logical_not<T> //逻辑非

示例：

Summary: the most commonly used relational functor is greater<> (greater than)

Logical Functors

Description:

• Implement logical operations

Function prototypes:

• template<class T> bool logical_and<T> //logical and
• template<class T> bool logical_or<T> //logical or
• template<class T> bool logical_not<T> //logical not

Example:

#include <vector>
#include <functional>
#include <algorithm>
void test01()
{
	vector<bool> v;
	v.push_back(true);
	v.push_back(false);
	v.push_back(true);
	v.push_back(false);

	for (vector<bool>::iterator it = v.begin();it!= v.end();it++)
	{
		cout << *it << " ";
	}
	cout << endl;

	//逻辑非  将v容器搬运到v2中，并执行逻辑非运算
	vector<bool> v2;
	v2.resize(v.size());
	transform(v.begin(), v.end(),  v2.begin(), logical_not<bool>());
	for (vector<bool>::iterator it = v2.begin(); it != v2.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：逻辑仿函数实际应用较少，了解即可

STL- 常用算法

概述:

• 算法主要是由头文件<algorithm> <functional> <numeric>组成。

• <algorithm>是所有STL头文件中最大的一个，范围涉及到比较、 交换、查找、遍历操作、复制、修改等等

• <numeric>体积很小，只包括几个在序列上面进行简单数学运算的模板函数

• <functional>定义了一些模板类,用以声明函数对象。

常用遍历算法

学习目标：

• 掌握常用的遍历算法

算法简介：

• for_each //遍历容器
• transform //搬运容器到另一个容器中

for_each

功能描述：

• 实现遍历容器

函数原型：

• for_each(iterator beg, iterator end, _func);

  // 遍历算法 遍历容器元素

  // beg 开始迭代器

  // end 结束迭代器

  // _func 函数或者函数对象

示例：

Summary: logical functors are rarely used in practice; just understand them

STL - Common Algorithms

Overview:

• Algorithms mainly consist of the header files <algorithm>, <functional>, and <numeric>

• <algorithm> is the largest of all STL header files, covering comparison, swapping, searching, traversal operations, copying, modification, etc.

• <numeric> is very small, containing only a few template functions for simple mathematical operations on sequences

• <functional> defines some template classes for declaring function objects

Common Traversal Algorithms

Learning objectives:

• Master the common traversal algorithms

Algorithm introduction:

• for_each //traverse the container
• transform //move the container to another container

for_each

Description:

• Traverse the container

Function prototypes:

• for_each(iterator beg, iterator end, _func);

  // traversal algorithm, traverses the container elements

  // beg start iterator

  // end end iterator

  // _func function or function object

Example:

#include <algorithm>
#include <vector>

//普通函数
void print01(int val) 
{
	cout << val << " ";
}
//函数对象
class print02 
{
 public:
	void operator()(int val) 
	{
		cout << val << " ";
	}
};

//for_each算法基本用法
void test01() {

	vector<int> v;
	for (int i = 0; i < 10; i++) 
	{
		v.push_back(i);
	}

	//遍历算法
	for_each(v.begin(), v.end(), print01);
	cout << endl;

	for_each(v.begin(), v.end(), print02());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**for_each在实际开发中是最常用遍历算法，需要熟练掌握

transform

功能描述：

• 搬运容器到另一个容器中

函数原型：

• transform(iterator beg1, iterator end1, iterator beg2, _func);

//beg1 源容器开始迭代器

//end1 源容器结束迭代器

//beg2 目标容器开始迭代器

//_func 函数或者函数对象

示例：

Summary: for_each is the most commonly used traversal algorithm in real development and needs to be mastered skillfully

transform

Description:

• Move the container to another container

Function prototypes:

• transform(iterator beg1, iterator end1, iterator beg2, _func);

//beg1 start iterator of the source container

//end1 end iterator of the source container

//beg2 start iterator of the target container

//_func function or function object

Example:

#include<vector>
#include<algorithm>

//常用遍历算法  搬运 transform

class TransForm
{
public:
	int operator()(int val)
	{
		return val;
	}

};

class MyPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int>v;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	vector<int>vTarget; //目标容器

	vTarget.resize(v.size()); // 目标容器需要提前开辟空间

	transform(v.begin(), v.end(), vTarget.begin(), TransForm());

	for_each(vTarget.begin(), vTarget.end(), MyPrint());
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结： 搬运的目标容器必须要提前开辟空间，否则无法正常搬运

常用查找算法

学习目标：

• 掌握常用的查找算法

算法简介：

• find //查找元素
• find_if //按条件查找元素
• adjacent_find //查找相邻重复元素
• binary_search //二分查找法
• count //统计元素个数
• count_if //按条件统计元素个数

find

功能描述：

• 查找指定元素，找到返回指定元素的迭代器，找不到返回结束迭代器end()

函数原型：

• find(iterator beg, iterator end, value);

  // 按值查找元素，找到返回指定位置迭代器，找不到返回结束迭代器位置

  // beg 开始迭代器

  // end 结束迭代器

  // value 查找的元素

示例：

Summary: the target container of the transfer must reserve space in advance, otherwise it cannot be transferred normally

Common Search Algorithms

Learning objectives:

• Master the common search algorithms

Algorithm introduction:

• find //find an element
• find_if //find elements by condition
• adjacent_find //find adjacent duplicate elements
• binary_search //binary search
• count //count the number of elements
• count_if //count the number of elements by condition

find

Description:

• Find a specified element; return the iterator of the specified element if found, or the end iterator end() if not found

Function prototypes:

• find(iterator beg, iterator end, value);

  // find the element by value; return the iterator at the specified position if found, or the end iterator position if not found

  // beg start iterator

  // end end iterator

  // value the element to find

Example:

#include <algorithm>
#include <vector>
#include <string>
void test01() {

	vector<int> v;
	for (int i = 0; i < 10; i++) {
		v.push_back(i + 1);
	}
	//查找容器中是否有 5 这个元素
	vector<int>::iterator it = find(v.begin(), v.end(), 5);
	if (it == v.end()) 
	{
		cout << "没有找到!" << endl;
	}
	else 
	{
		cout << "找到:" << *it << endl;
	}
}

class Person {
public:
	Person(string name, int age) 
	{
		this->m_Name = name;
		this->m_Age = age;
	}
	//重载==
	bool operator==(const Person& p) 
	{
		if (this->m_Name == p.m_Name && this->m_Age == p.m_Age) 
		{
			return true;
		}
		return false;
	}

public:
	string m_Name;
	int m_Age;
};

void test02() {

	vector<Person> v;

	//创建数据
	Person p1("aaa", 10);
	Person p2("bbb", 20);
	Person p3("ccc", 30);
	Person p4("ddd", 40);

	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);

	vector<Person>::iterator it = find(v.begin(), v.end(), p2);
	if (it == v.end()) 
	{
		cout << "没有找到!" << endl;
	}
	else 
	{
		cout << "找到姓名:" << it->m_Name << " 年龄: " << it->m_Age << endl;
	}
}

总结： 利用find可以在容器中找指定的元素，返回值是迭代器

find_if

功能描述：

• 按条件查找元素

函数原型：

• find_if(iterator beg, iterator end, _Pred);

  // 按值查找元素，找到返回指定位置迭代器，找不到返回结束迭代器位置

  // beg 开始迭代器

  // end 结束迭代器

  // _Pred 函数或者谓词（返回bool类型的仿函数）

示例：

Summary: find can be used to find a specified element in a container, and the return value is an iterator

find_if

Description:

• Find elements by condition

Function prototypes:

• find_if(iterator beg, iterator end, _Pred);

  // find the element by value; return the iterator at the specified position if found, or the end iterator position if not found

  // beg start iterator

  // end end iterator

  // _Pred function or predicate (a functor that returns bool)

Example:

#include <algorithm>
#include <vector>
#include <string>

//内置数据类型
class GreaterFive
{
public:
	bool operator()(int val)
	{
		return val > 5;
	}
};

void test01() {

	vector<int> v;
	for (int i = 0; i < 10; i++) {
		v.push_back(i + 1);
	}

	vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
	if (it == v.end()) {
		cout << "没有找到!" << endl;
	}
	else {
		cout << "找到大于5的数字:" << *it << endl;
	}
}

//自定义数据类型
class Person {
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}
public:
	string m_Name;
	int m_Age;
};

class Greater20
{
public:
	bool operator()(Person &p)
	{
		return p.m_Age > 20;
	}

};

void test02() {

	vector<Person> v;

	//创建数据
	Person p1("aaa", 10);
	Person p2("bbb", 20);
	Person p3("ccc", 30);
	Person p4("ddd", 40);

	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);

	vector<Person>::iterator it = find_if(v.begin(), v.end(), Greater20());
	if (it == v.end())
	{
		cout << "没有找到!" << endl;
	}
	else
	{
		cout << "找到姓名:" << it->m_Name << " 年龄: " << it->m_Age << endl;
	}
}

int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结：find_if按条件查找使查找更加灵活，提供的仿函数可以改变不同的策略

adjacent_find

功能描述：

• 查找相邻重复元素

函数原型：

• adjacent_find(iterator beg, iterator end);

  // 查找相邻重复元素,返回相邻元素的第一个位置的迭代器

  // beg 开始迭代器

  // end 结束迭代器

示例：

Summary: find can be used to find a specified element in a container, and the return value is an iterator

find_if

Description:

• Find elements by condition

Function prototypes:

• find_if(iterator beg, iterator end, _Pred);

  // find the element by value; return the iterator at the specified position if found, or the end iterator position if not found

  // beg start iterator

  // end end iterator

  // _Pred function or predicate (a functor that returns bool)

Example:

#include <algorithm>
#include <vector>

void test01()
{
	vector<int> v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(5);
	v.push_back(2);
	v.push_back(4);
	v.push_back(4);
	v.push_back(3);

	//查找相邻重复元素
	vector<int>::iterator it = adjacent_find(v.begin(), v.end());
	if (it == v.end()) {
		cout << "找不到!" << endl;
	}
	else {
		cout << "找到相邻重复元素为:" << *it << endl;
	}
}

总结：面试题中如果出现查找相邻重复元素，记得用STL中的adjacent_find算法

binary_search

功能描述：

• 查找指定元素是否存在

函数原型：

• bool binary_search(iterator beg, iterator end, value);

  // 查找指定的元素，查到 返回true 否则false

  // 注意: 在无序序列中不可用

  // beg 开始迭代器

  // end 结束迭代器

  // value 查找的元素

示例：

Summary: find_if makes searching more flexible with conditions, and the provided functors can change different strategies

adjacent_find

Description:

• Find adjacent duplicate elements

Function prototypes:

• adjacent_find(iterator beg, iterator end);

  // find adjacent duplicate elements, return the iterator of the first position of the adjacent elements

  // beg start iterator

  // end end iterator

Example:

#include <algorithm>
#include <vector>

void test01()
{
	vector<int>v;

	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}
	//二分查找
	bool ret = binary_search(v.begin(), v.end(),2);
	if (ret)
	{
		cout << "找到了" << endl;
	}
	else
	{
		cout << "未找到" << endl;
	}
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**二分查找法查找效率很高，值得注意的是查找的容器中元素必须的有序序列

count

功能描述：

• 统计元素个数

函数原型：

• count(iterator beg, iterator end, value);

  // 统计元素出现次数

  // beg 开始迭代器

  // end 结束迭代器

  // value 统计的元素

示例：

Summary: if finding adjacent duplicate elements appears in an interview question, remember to use the adjacent_find algorithm in STL

binary_search

Description:

• Check whether a specified element exists

Function prototypes:

• bool binary_search(iterator beg, iterator end, value);

  // find the specified element; return true if found, otherwise false

  // note: cannot be used on unordered sequences

  // beg start iterator

  // end end iterator

  // value the element to find

Example:

#include <algorithm>
#include <vector>

//内置数据类型
void test01()
{
	vector<int> v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(4);
	v.push_back(5);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);

	int num = count(v.begin(), v.end(), 4);

	cout << "4的个数为： " << num << endl;
}

//自定义数据类型
class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}
	bool operator==(const Person & p)
	{
		if (this->m_Age == p.m_Age)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	string m_Name;
	int m_Age;
};

void test02()
{
	vector<Person> v;

	Person p1("刘备", 35);
	Person p2("关羽", 35);
	Person p3("张飞", 35);
	Person p4("赵云", 30);
	Person p5("曹操", 25);

	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);
	v.push_back(p5);
    
    Person p("诸葛亮",35);

	int num = count(v.begin(), v.end(), p);
	cout << "num = " << num << endl;
}
int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

总结： 统计自定义数据类型时候，需要配合重载 operator==

count_if

功能描述：

• 按条件统计元素个数

函数原型：

• count_if(iterator beg, iterator end, _Pred);

  // 按条件统计元素出现次数

  // beg 开始迭代器

  // end 结束迭代器

  // _Pred 谓词

示例：

Summary: binary search is very efficient, but note that the elements in the container must be an ordered sequence

count

Description:

• Count the number of elements

Function prototypes:

• count(iterator beg, iterator end, value);

  // count the number of occurrences of the element

  // beg start iterator

  // end end iterator

  // value the element to count

Example:

#include <algorithm>
#include <vector>

class Greater4
{
public:
	bool operator()(int val)
	{
		return val >= 4;
	}
};

//内置数据类型
void test01()
{
	vector<int> v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(4);
	v.push_back(5);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);

	int num = count_if(v.begin(), v.end(), Greater4());

	cout << "大于4的个数为： " << num << endl;
}

//自定义数据类型
class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	string m_Name;
	int m_Age;
};

class AgeLess35
{
public:
	bool operator()(const Person &p)
	{
		return p.m_Age < 35;
	}
};
void test02()
{
	vector<Person> v;

	Person p1("刘备", 35);
	Person p2("关羽", 35);
	Person p3("张飞", 35);
	Person p4("赵云", 30);
	Person p5("曹操", 25);

	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);
	v.push_back(p5);

	int num = count_if(v.begin(), v.end(), AgeLess35());
	cout << "小于35岁的个数：" << num << endl;
}


int main() {

	//test01();

	test02();

	system("pause");

	return 0;
}

**总结：**按值统计用count，按条件统计用count_if

常用排序算法

学习目标：

• 掌握常用的排序算法

算法简介：

• sort //对容器内元素进行排序
• random_shuffle //洗牌 指定范围内的元素随机调整次序
• merge // 容器元素合并，并存储到另一容器中
• reverse // 反转指定范围的元素

sort

功能描述：

• 对容器内元素进行排序

函数原型：

• sort(iterator beg, iterator end, _Pred);

  // 按值查找元素，找到返回指定位置迭代器，找不到返回结束迭代器位置

  // beg 开始迭代器

  // end 结束迭代器

  // _Pred 谓词

示例：

Summary: use count to count by value, and count_if to count by condition

Common Sorting Algorithms

Learning objectives:

• Master the common sorting algorithms

Algorithm introduction:

• sort //sort the elements in the container
• random_shuffle //shuffle; randomly adjust the order of elements in the specified range
• merge //merge container elements and store them in another container
• reverse //reverse the elements in the specified range

sort

Description:

• Sort the elements in the container

Function prototypes:

• sort(iterator beg, iterator end, _Pred);

  // find the element by value; return the iterator at the specified position if found, or the end iterator position if not found

  // beg start iterator

  // end end iterator

  // _Pred predicate

Example:

#include <algorithm>
#include <vector>

void myPrint(int val)
{
	cout << val << " ";
}

void test01() {
	vector<int> v;
	v.push_back(10);
	v.push_back(30);
	v.push_back(50);
	v.push_back(20);
	v.push_back(40);

	//sort默认从小到大排序
	sort(v.begin(), v.end());
	for_each(v.begin(), v.end(), myPrint);
	cout << endl;

	//从大到小排序
	sort(v.begin(), v.end(), greater<int>());
	for_each(v.begin(), v.end(), myPrint);
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**sort属于开发中最常用的算法之一，需熟练掌握

random_shuffle

功能描述：

• 洗牌 指定范围内的元素随机调整次序

函数原型：

• random_shuffle(iterator beg, iterator end);

  // 指定范围内的元素随机调整次序

  // beg 开始迭代器

  // end 结束迭代器

示例：

Summary: sort is one of the most commonly used algorithms in development and needs to be mastered skillfully

random_shuffle

Description:

• Shuffle; randomly adjust the order of elements in the specified range

Function prototypes:

• random_shuffle(iterator beg, iterator end);

  // randomly adjust the order of elements in the specified range

  // beg start iterator

  // end end iterator

Example:

#include <algorithm>
#include <vector>
#include <ctime>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	srand((unsigned int)time(NULL));
	vector<int> v;
	for(int i = 0 ; i < 10;i++)
	{
		v.push_back(i);
	}
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;

	//打乱顺序
	random_shuffle(v.begin(), v.end());
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**random_shuffle洗牌算法比较实用，使用时记得加随机数种子

merge

功能描述：

• 两个容器元素合并，并存储到另一容器中

函数原型：

• merge(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // 容器元素合并，并存储到另一容器中

  // 注意: 两个容器必须是有序的

  // beg1 容器1开始迭代器
  // end1 容器1结束迭代器
  // beg2 容器2开始迭代器
  // end2 容器2结束迭代器
  // dest 目标容器开始迭代器

示例：

Summary: sort is one of the most commonly used algorithms in development and needs to be mastered skillfully

random_shuffle

Description:

• Shuffle; randomly adjust the order of elements in the specified range

Function prototypes:

• random_shuffle(iterator beg, iterator end);

  // randomly adjust the order of elements in the specified range

  // beg start iterator

  // end end iterator

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10 ; i++) 
    {
		v1.push_back(i);
		v2.push_back(i + 1);
	}

	vector<int> vtarget;
	//目标容器需要提前开辟空间
	vtarget.resize(v1.size() + v2.size());
	//合并  需要两个有序序列
	merge(v1.begin(), v1.end(), v2.begin(), v2.end(), vtarget.begin());
	for_each(vtarget.begin(), vtarget.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**merge合并的两个容器必须的有序序列

reverse

功能描述：

• 将容器内元素进行反转

函数原型：

• reverse(iterator beg, iterator end);

  // 反转指定范围的元素

  // beg 开始迭代器

  // end 结束迭代器

示例：

Summary: the random_shuffle shuffling algorithm is quite practical; remember to add a random number seed when using it

merge

Description:

• Merge the elements of two containers and store them in another container

Function prototypes:

• merge(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // merge the container elements and store them in another container

  // note: the two containers must be ordered

  // beg1 start iterator of container 1
  // end1 end iterator of container 1
  // beg2 start iterator of container 2
  // end2 end iterator of container 2
  // dest start iterator of the target container

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(30);
	v.push_back(50);
	v.push_back(20);
	v.push_back(40);

	cout << "反转前： " << endl;
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;

	cout << "反转后： " << endl;

	reverse(v.begin(), v.end());
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**reverse反转区间内元素，面试题可能涉及到

常用拷贝和替换算法

学习目标：

• 掌握常用的拷贝和替换算法

算法简介：

• copy // 容器内指定范围的元素拷贝到另一容器中
• replace // 将容器内指定范围的旧元素修改为新元素
• replace_if // 容器内指定范围满足条件的元素替换为新元素
• swap // 互换两个容器的元素

copy

功能描述：

• 容器内指定范围的元素拷贝到另一容器中

函数原型：

• copy(iterator beg, iterator end, iterator dest);

  // 按值查找元素，找到返回指定位置迭代器，找不到返回结束迭代器位置

  // beg 开始迭代器

  // end 结束迭代器

  // dest 目标起始迭代器

示例：

Summary: reverse reverses the elements in the range; it may appear in interview questions

Common Copy and Replace Algorithms

Learning objectives:

• Master the common copy and replace algorithms

Algorithm introduction:

• copy //copy the elements in the specified range of the container to another container
• replace //replace the old elements in the specified range of the container with new elements
• replace_if //replace the elements meeting the condition in the specified range of the container with new elements
• swap //swap the elements of two containers

copy

Description:

• Copy the elements in the specified range of the container to another container

Function prototypes:

• copy(iterator beg, iterator end, iterator dest);

  // find the element by value; return the iterator at the specified position if found, or the end iterator position if not found

  // beg start iterator

  // end end iterator

  // dest start iterator of the target

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i + 1);
	}
	vector<int> v2;
	v2.resize(v1.size());
	copy(v1.begin(), v1.end(), v2.begin());

	for_each(v2.begin(), v2.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**利用copy算法在拷贝时，目标容器记得提前开辟空间

replace

功能描述：

• 将容器内指定范围的旧元素修改为新元素

函数原型：

• replace(iterator beg, iterator end, oldvalue, newvalue);

  // 将区间内旧元素 替换成 新元素

  // beg 开始迭代器

  // end 结束迭代器

  // oldvalue 旧元素

  // newvalue 新元素

示例：

Summary: when copying with the copy algorithm, remember to reserve space for the target container in advance

replace

Description:

• Replace the old elements in the specified range of the container with new elements

Function prototypes:

• replace(iterator beg, iterator end, oldvalue, newvalue);

  // replace the old elements in the range with new elements

  // beg start iterator

  // end end iterator

  // oldvalue the old element

  // newvalue the new element

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v;
	v.push_back(20);
	v.push_back(30);
	v.push_back(20);
	v.push_back(40);
	v.push_back(50);
	v.push_back(10);
	v.push_back(20);

	cout << "替换前：" << endl;
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;

	//将容器中的20 替换成 2000
	cout << "替换后：" << endl;
	replace(v.begin(), v.end(), 20,2000);
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**replace会替换区间内满足条件的元素

replace_if

功能描述:

• 将区间内满足条件的元素，替换成指定元素

函数原型：

• replace_if(iterator beg, iterator end, _pred, newvalue);

  // 按条件替换元素，满足条件的替换成指定元素

  // beg 开始迭代器

  // end 结束迭代器

  // _pred 谓词

  // newvalue 替换的新元素

示例：

Summary: when copying with the copy algorithm, remember to reserve space for the target container in advance

replace

Description:

• Replace the old elements in the specified range of the container with new elements

Function prototypes:

• replace(iterator beg, iterator end, oldvalue, newvalue);

  // replace the old elements in the range with new elements

  // beg start iterator

  // end end iterator

  // oldvalue the old element

  // newvalue the new element

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

class ReplaceGreater30
{
public:
	bool operator()(int val)
	{
		return val >= 30;
	}

};

void test01()
{
	vector<int> v;
	v.push_back(20);
	v.push_back(30);
	v.push_back(20);
	v.push_back(40);
	v.push_back(50);
	v.push_back(10);
	v.push_back(20);

	cout << "替换前：" << endl;
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;

	//将容器中大于等于的30 替换成 3000
	cout << "替换后：" << endl;
	replace_if(v.begin(), v.end(), ReplaceGreater30(), 3000);
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**replace_if按条件查找，可以利用仿函数灵活筛选满足的条件

swap

功能描述：

• 互换两个容器的元素

函数原型：

• swap(container c1, container c2);

  // 互换两个容器的元素

  // c1容器1

  // c2容器2

示例：

Summary: replace replaces the elements meeting the condition in the range

replace_if

Description:

• Replace the elements meeting the condition in the range with the specified element

Function prototypes:

• replace_if(iterator beg, iterator end, _pred, newvalue);

  // replace elements by condition; replace the ones meeting the condition with the specified element

  // beg start iterator

  // end end iterator

  // _pred predicate

  // newvalue the new element to replace with

Example:

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i);
		v2.push_back(i+100);
	}

	cout << "交换前： " << endl;
	for_each(v1.begin(), v1.end(), myPrint());
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint());
	cout << endl;

	cout << "交换后： " << endl;
	swap(v1, v2);
	for_each(v1.begin(), v1.end(), myPrint());
	cout << endl;
	for_each(v2.begin(), v2.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**swap交换容器时，注意交换的容器要同种类型

常用算术生成算法

学习目标：

• 掌握常用的算术生成算法

注意：

• 算术生成算法属于小型算法，使用时包含的头文件为 #include <numeric>

算法简介：

• accumulate // 计算容器元素累计总和

• fill // 向容器中添加元素

accumulate

功能描述：

• 计算区间内 容器元素累计总和

函数原型：

• accumulate(iterator beg, iterator end, value);

  // 计算容器元素累计总和

  // beg 开始迭代器

  // end 结束迭代器

  // value 起始值

示例：

Summary: when swapping containers with swap, note that the containers must be of the same type

Common Arithmetic Generation Algorithms

Learning objectives:

• Master the common arithmetic generation algorithms

Note:

• Arithmetic generation algorithms are small algorithms; the header file to include is #include <numeric>

Algorithm introduction:

• accumulate //calculate the cumulative sum of container elements

• fill //fill elements into the container

accumulate

Description:

• Calculate the cumulative sum of container elements in the range

Function prototypes:

• accumulate(iterator beg, iterator end, value);

  // calculate the cumulative sum of container elements

  // beg start iterator

  // end end iterator

  // value the initial value

Example:

#include <numeric>
#include <vector>
void test01()
{
	vector<int> v;
	for (int i = 0; i <= 100; i++) {
		v.push_back(i);
	}

	int total = accumulate(v.begin(), v.end(), 0);

	cout << "total = " << total << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**accumulate使用时头文件注意是 numeric，这个算法很实用

fill

功能描述：

• 向容器中填充指定的元素

函数原型：

• fill(iterator beg, iterator end, value);

  // 向容器中填充元素

  // beg 开始迭代器

  // end 结束迭代器

  // value 填充的值

示例：

Summary: note that the header file for accumulate is numeric; this algorithm is very practical

fill

Description:

• Fill the container with the specified elements

Function prototypes:

• fill(iterator beg, iterator end, value);

  // fill the container with elements

  // beg start iterator

  // end end iterator

  // value the value to fill

Example:

#include <numeric>
#include <vector>
#include <algorithm>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{

	vector<int> v;
	v.resize(10);
	//填充
	fill(v.begin(), v.end(), 100);

	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

**总结：**利用fill可以将容器区间内元素填充为 指定的值

常用集合算法

学习目标：

• 掌握常用的集合算法

算法简介：

• set_intersection // 求两个容器的交集

• set_union // 求两个容器的并集

• set_difference // 求两个容器的差集

set_intersection

功能描述：

• 求两个容器的交集

函数原型：

• set_intersection(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // 求两个集合的交集

  // 注意:两个集合必须是有序序列

  // beg1 容器1开始迭代器
  // end1 容器1结束迭代器
  // beg2 容器2开始迭代器
  // end2 容器2结束迭代器
  // dest 目标容器开始迭代器

示例：

Summary: fill can be used to fill the elements in the container range with a specified value

Common Set Algorithms

Learning objectives:

• Master the common set algorithms

Algorithm introduction:

• set_intersection //find the intersection of two containers

• set_union //find the union of two containers

• set_difference //find the difference of two containers

set_intersection

Description:

• Find the intersection of two containers

Function prototypes:

• set_intersection(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // find the intersection of two sets

  // note: the two sets must be ordered sequences

  // beg1 start iterator of container 1
  // end1 end iterator of container 1
  // beg2 start iterator of container 2
  // end2 end iterator of container 2
  // dest start iterator of the target container

Example:

#include <vector>
#include <algorithm>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++)
    {
		v1.push_back(i);
		v2.push_back(i+5);
	}

	vector<int> vTarget;
	//取两个里面较小的值给目标容器开辟空间
	vTarget.resize(min(v1.size(), v2.size()));

	//返回目标容器的最后一个元素的迭代器地址
	vector<int>::iterator itEnd = 
        set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(), vTarget.begin());

	for_each(vTarget.begin(), itEnd, myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 求交集的两个集合必须的有序序列
• 目标容器开辟空间需要从两个容器中取小值
• set_intersection返回值既是交集中最后一个元素的位置

set_union

功能描述：

• 求两个集合的并集

函数原型：

• set_union(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // 求两个集合的并集

  // 注意:两个集合必须是有序序列

  // beg1 容器1开始迭代器
  // end1 容器1结束迭代器
  // beg2 容器2开始迭代器
  // end2 容器2结束迭代器
  // dest 目标容器开始迭代器

示例：

Summary:

• The two sets for finding the intersection must be ordered sequences
• The target container needs to reserve space using the smaller value of the two containers
• The return value of set_intersection is the position of the last element in the intersection

set_union

Description:

• Find the union of two sets

Function prototypes:

• set_union(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // find the union of two sets

  // note: the two sets must be ordered sequences

  // beg1 start iterator of container 1
  // end1 end iterator of container 1
  // beg2 start iterator of container 2
  // end2 end iterator of container 2
  // dest start iterator of the target container

Example:

#include <vector>
#include <algorithm>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i);
		v2.push_back(i+5);
	}

	vector<int> vTarget;
	//取两个容器的和给目标容器开辟空间
	vTarget.resize(v1.size() + v2.size());

	//返回目标容器的最后一个元素的迭代器地址
	vector<int>::iterator itEnd = 
        set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), vTarget.begin());

	for_each(vTarget.begin(), itEnd, myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 求并集的两个集合必须的有序序列
• 目标容器开辟空间需要两个容器相加
• set_union返回值既是并集中最后一个元素的位置

set_difference

功能描述：

• 求两个集合的差集

函数原型：

• set_difference(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // 求两个集合的差集

  // 注意:两个集合必须是有序序列

  // beg1 容器1开始迭代器
  // end1 容器1结束迭代器
  // beg2 容器2开始迭代器
  // end2 容器2结束迭代器
  // dest 目标容器开始迭代器

示例：

Summary:

• The two sets for finding the union must be ordered sequences
• The target container needs to reserve space using the sum of the two containers
• The return value of set_union is the position of the last element in the union

set_difference

Description:

• Find the difference of two sets

Function prototypes:

• set_difference(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

  // find the difference of two sets

  // note: the two sets must be ordered sequences

  // beg1 start iterator of container 1
  // end1 end iterator of container 1
  // beg2 start iterator of container 2
  // end2 end iterator of container 2
  // dest start iterator of the target container

Example:

#include <vector>
#include <algorithm>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10; i++) {
		v1.push_back(i);
		v2.push_back(i+5);
	}

	vector<int> vTarget;
	//取两个里面较大的值给目标容器开辟空间
	vTarget.resize( max(v1.size() , v2.size()));

	//返回目标容器的最后一个元素的迭代器地址
	cout << "v1与v2的差集为： " << endl;
	vector<int>::iterator itEnd = 
        set_difference(v1.begin(), v1.end(), v2.begin(), v2.end(), vTarget.begin());
	for_each(vTarget.begin(), itEnd, myPrint());
	cout << endl;


	cout << "v2与v1的差集为： " << endl;
	itEnd = set_difference(v2.begin(), v2.end(), v1.begin(), v1.end(), vTarget.begin());
	for_each(vTarget.begin(), itEnd, myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

总结：

• 求差集的两个集合必须的有序序列
• 目标容器开辟空间需要从两个容器取较大值
• set_difference返回值既是差集中最后一个元素的位置

Summary:

• The two sets for finding the difference must be ordered sequences
• The target container needs to reserve space using the larger value of the two containers
• The return value of set_difference is the position of the last element in the difference