C++初识

第一个C++程序

编写一个C++程序总共分为4个步骤

  • 创建项目
  • 创建文件
  • 编写代码
  • 运行程序

创建项目

​ Visual Studio是我们用来编写C++程序的主要工具，我们先将它打开

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创建文件

右键源文件，选择添加->新建项

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给C++文件起个名称，然后点击添加即可。

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编写代码

Getting Started with C++

Your First C++ Program

Writing a C++ program involves 4 steps in total

  • Create a project
  • Create a file
  • Write the code
  • Run the program

Creating a Project

​ Visual Studio is the main tool we use to write C++ programs, so let’s open it first

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Creating a File

Right-click the Source Files, choose Add -> New Item

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Give the C++ file a name, then click Add.

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Writing the Code

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#include<iostream>
using namespace std;

int main() {

	cout << "Hello world" << endl;

	system("pause");

	return 0;
}

运行程序

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Running the Program

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注释

作用：在代码中加一些说明和解释，方便自己或其他程序员程序员阅读代码

两种格式

  1. 单行注释：// 描述信息
    • 通常放在一行代码的上方，或者一条语句的末尾，对该行代码说明
  2. 多行注释： /* 描述信息 */
    • 通常放在一段代码的上方，对该段代码做整体说明

提示：编译器在编译代码时，会忽略注释的内容

Comments

Purpose: add some notes and explanations to the code, making it easier for yourself or other programmers to read

Two formats

  1. Single-line comment: // description
    • Usually placed above a line of code, or at the end of a statement, to explain that line of code
  2. Multi-line comment: /* description */
    • Usually placed above a block of code, to give an overall explanation of that block of code

Tip: the compiler ignores comments when compiling code

变量

作用：给一段指定的内存空间起名，方便操作这段内存

语法：数据类型 变量名 = 初始值;

示例：

Variables

Purpose: give a name to a specified block of memory so it is easier to operate on that memory

Syntax: data type variable name = initial value;

Example:

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#include<iostream>
using namespace std;

int main() {

	//变量的定义
	//语法：数据类型  变量名 = 初始值

	int a = 10;

	cout << "a = " << a << endl;
	
	system("pause");

	return 0;
}

注意：C++在创建变量时，必须给变量一个初始值，否则会报错

常量

作用：用于记录程序中不可更改的数据

C++定义常量两种方式

  1. #define 宏常量： #define 常量名 常量值

    • 通常在文件上方定义，表示一个常量

  2. const修饰的变量 const 数据类型 常量名 = 常量值

    • 通常在变量定义前加关键字const，修饰该变量为常量，不可修改

示例：

Note: when creating a variable in C++, you must give it an initial value, otherwise an error will occur

Constants

Purpose: used to record data that cannot be changed in the program

There are two ways to define constants in C++

  1. #define macro constant: #define constant name constant value

    • Usually defined at the top of the file, representing a constant

  2. const-modified variable const data type constant name = constant value

    • Usually add the keyword const before the variable definition, modifying the variable into a constant that cannot be changed

Example:

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//1、宏常量
#define day 7

int main() {

	cout << "一周里总共有 " << day << " 天" << endl;
	//day = 8;  //报错，宏常量不可以修改

	//2、const修饰变量
	const int month = 12;
	cout << "一年里总共有 " << month << " 个月份" << endl;
	//month = 24; //报错，常量是不可以修改的
	
	
	system("pause");

	return 0;
}

关键字

**作用：**关键字是C++中预先保留的单词（标识符）

  • 在定义变量或者常量时候，不要用关键字

C++关键字如下：

asm do if return typedef
auto double inline short typeid
bool dynamic_cast int signed typename
break else long sizeof union
case enum mutable static unsigned
catch explicit namespace static_cast using
char export new struct virtual
class extern operator switch void
const false private template volatile
const_cast float protected this wchar_t
continue for public throw while
default friend register true
delete goto reinterpret_cast try

提示：在给变量或者常量起名称时候，不要用C++得关键字，否则会产生歧义。

Keywords

Purpose: keywords are words (identifiers) pre-reserved in C++

  • Do not use keywords when defining variables or constants

The C++ keywords are as follows:

asm do if return typedef
auto double inline short typeid
bool dynamic_cast int signed typename
break else long sizeof union
case enum mutable static unsigned
catch explicit namespace static_cast using
char export new struct virtual
class extern operator switch void
const false private template volatile
const_cast float protected this wchar_t
continue for public throw while
default friend register true
delete goto reinterpret_cast try

Tip: when naming variables or constants, do not use C++ keywords, otherwise ambiguity will arise.

标识符命名规则

作用：C++规定给标识符（变量、常量）命名时，有一套自己的规则

  • 标识符不能是关键字
  • 标识符只能由字母、数字、下划线组成
  • 第一个字符必须为字母或下划线
  • 标识符中字母区分大小写

建议：给标识符命名时，争取做到见名知意的效果，方便自己和他人的阅读

Identifier Naming Rules

Purpose: C++ specifies that when naming identifiers (variables, constants), there is a set of rules to follow

  • Identifiers cannot be keywords
  • Identifiers can only consist of letters, digits, and underscores
  • The first character must be a letter or an underscore
  • Identifiers are case-sensitive

Suggestion: when naming identifiers, try to make the name self-explanatory, so it is easier for yourself and others to read

数据类型

C++规定在创建一个变量或者常量时，必须要指定出相应的数据类型，否则无法给变量分配内存

Data Types

C++ requires that when creating a variable or constant, the corresponding data type must be specified, otherwise memory cannot be allocated for the variable

整型

作用：整型变量表示的是整数类型的数据

C++中能够表示整型的类型有以下几种方式，区别在于所占内存空间不同：

数据类型 占用空间 取值范围
short(短整型) 2字节 (-2^15 ~ 2^15-1)
int(整型) 4字节 (-2^31 ~ 2^31-1)
long(长整形) Windows为4字节，Linux为4字节(32位)，8字节(64位) (-2^31 ~ 2^31-1)
long long(长长整形) 8字节 (-2^63 ~ 2^63-1)

Integer Types

Purpose: integer variables represent integer type data

C++ provides the following types to represent integers, which differ in the amount of memory they occupy:

Data Type Memory Occupied Value Range
short (short integer) 2 bytes (-2^15 ~ 2^15-1)
int (integer) 4 bytes (-2^31 ~ 2^31-1)
long (long integer) 4 bytes on Windows, 4 bytes (32-bit) or 8 bytes (64-bit) on Linux (-2^31 ~ 2^31-1)
long long (long long integer) 8 bytes (-2^63 ~ 2^63-1)

sizeof关键字

**作用：**利用sizeof关键字可以统计数据类型所占内存大小

语法： sizeof( 数据类型 / 变量)

示例：

The sizeof Keyword

Purpose: the sizeof keyword can be used to calculate the amount of memory occupied by a data type

Syntax: sizeof( data type / variable)

Example:

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int main() {

	cout << "short 类型所占内存空间为： " << sizeof(short) << endl;

	cout << "int 类型所占内存空间为： " << sizeof(int) << endl;

	cout << "long 类型所占内存空间为： " << sizeof(long) << endl;

	cout << "long long 类型所占内存空间为： " << sizeof(long long) << endl;

	system("pause");

	return 0;
}

整型结论：short < int <= long <= long long

Integer type conclusion: short < int <= long <= long long

实型（浮点型）

作用：用于表示小数

浮点型变量分为两种：

  1. 单精度float
  2. 双精度double

两者的区别在于表示的有效数字范围不同。

数据类型 占用空间 有效数字范围
float 4字节 7位有效数字
double 8字节 15～16位有效数字

示例：

Floating-Point Types (Real Types)

Purpose: used to represent decimals

Floating-point variables are divided into two types:

  1. Single-precision float
  2. Double-precision double

The difference between them lies in the range of significant digits they can represent.

Data Type Memory Occupied Significant Digits
float 4 bytes 7 significant digits
double 8 bytes 15~16 significant digits

Example:

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int main() {

	float f1 = 3.14f;
	double d1 = 3.14;

	cout << f1 << endl;
	cout << d1<< endl;

	cout << "float  sizeof = " << sizeof(f1) << endl;
	cout << "double sizeof = " << sizeof(d1) << endl;

	//科学计数法
	float f2 = 3e2; // 3 * 10 ^ 2 
	cout << "f2 = " << f2 << endl;

	float f3 = 3e-2;  // 3 * 0.1 ^ 2
	cout << "f3 = " << f3 << endl;

	system("pause");

	return 0;
}

字符型

**作用：**字符型变量用于显示单个字符

语法：char ch = 'a';

注意1：在显示字符型变量时，用单引号将字符括起来，不要用双引号

注意2：单引号内只能有一个字符，不可以是字符串

  • C和C++中字符型变量只占用1个字节。
  • 字符型变量并不是把字符本身放到内存中存储，而是将对应的ASCII编码放入到存储单元

示例：

Character Type

Purpose: character-type variables are used to display a single character

Syntax: char ch = 'a';

Note 1: when displaying a character variable, enclose the character in single quotes, not double quotes

Note 2: only one character is allowed inside single quotes, not a string

  • In C and C++, a character variable occupies only 1 byte.
  • A character variable does not store the character itself in memory; instead, it stores the corresponding ASCII code in the memory unit

Example:

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int main() {
	
	char ch = 'a';
	cout << ch << endl;
	cout << sizeof(char) << endl;

	//ch = "abcde"; //错误，不可以用双引号
	//ch = 'abcde'; //错误，单引号内只能引用一个字符

	cout << (int)ch << endl;  //查看字符a对应的ASCII码
	ch = 97; //可以直接用ASCII给字符型变量赋值
	cout << ch << endl;

	system("pause");

	return 0;
}

ASCII码表格：

ASCII值 控制字符 ASCII值 字符 ASCII值 字符 ASCII值 字符
0 NUT 32 (space) 64 @ 96 、
1 SOH 33 ! 65 A 97 a
2 STX 34 " 66 B 98 b
3 ETX 35 # 67 C 99 c
4 EOT 36 $ 68 D 100 d
5 ENQ 37 % 69 E 101 e
6 ACK 38 & 70 F 102 f
7 BEL 39 , 71 G 103 g
8 BS 40 ( 72 H 104 h
9 HT 41 ) 73 I 105 i
10 LF 42 * 74 J 106 j
11 VT 43 + 75 K 107 k
12 FF 44 , 76 L 108 l
13 CR 45 - 77 M 109 m
14 SO 46 . 78 N 110 n
15 SI 47 / 79 O 111 o
16 DLE 48 0 80 P 112 p
17 DCI 49 1 81 Q 113 q
18 DC2 50 2 82 R 114 r
19 DC3 51 3 83 S 115 s
20 DC4 52 4 84 T 116 t
21 NAK 53 5 85 U 117 u
22 SYN 54 6 86 V 118 v
23 TB 55 7 87 W 119 w
24 CAN 56 8 88 X 120 x
25 EM 57 9 89 Y 121 y
26 SUB 58 : 90 Z 122 z
27 ESC 59 ; 91 [ 123 {
28 FS 60 < 92 / 124 |
29 GS 61 = 93 ] 125 }
30 RS 62 > 94 ^ 126 `
31 US 63 ? 95 _ 127 DEL

ASCII 码大致由以下两部分组成：

  • ASCII 非打印控制字符： ASCII 表上的数字 0-31 分配给了控制字符，用于控制像打印机等一些外围设备。
  • ASCII 打印字符：数字 32-126 分配给了能在键盘上找到的字符，当查看或打印文档时就会出现。

ASCII code table:

ASCII Control ASCII Char ASCII Char ASCII Char
0 NUT 32 (space) 64 @ 96 、
1 SOH 33 ! 65 A 97 a
2 STX 34 " 66 B 98 b
3 ETX 35 # 67 C 99 c
4 EOT 36 $ 68 D 100 d
5 ENQ 37 % 69 E 101 e
6 ACK 38 & 70 F 102 f
7 BEL 39 , 71 G 103 g
8 BS 40 ( 72 H 104 h
9 HT 41 ) 73 I 105 i
10 LF 42 * 74 J 106 j
11 VT 43 + 75 K 107 k
12 FF 44 , 76 L 108 l
13 CR 45 - 77 M 109 m
14 SO 46 . 78 N 110 n
15 SI 47 / 79 O 111 o
16 DLE 48 0 80 P 112 p
17 DCI 49 1 81 Q 113 q
18 DC2 50 2 82 R 114 r
19 DC3 51 3 83 S 115 s
20 DC4 52 4 84 T 116 t
21 NAK 53 5 85 U 117 u
22 SYN 54 6 86 V 118 v
23 TB 55 7 87 W 119 w
24 CAN 56 8 88 X 120 x
25 EM 57 9 89 Y 121 y
26 SUB 58 : 90 Z 122 z
27 ESC 59 ; 91 [ 123 {
28 FS 60 < 92 / 124 |
29 GS 61 = 93 ] 125 }
30 RS 62 > 94 ^ 126 `
31 US 63 ? 95 _ 127 DEL

The ASCII code table roughly consists of the following two parts:

  • ASCII non-printing control characters: numbers 0-31 on the ASCII table are assigned to control characters, used to control peripheral devices such as printers.
  • ASCII printable characters: numbers 32-126 are assigned to characters that can be found on the keyboard, which appear when viewing or printing documents.

转义字符

**作用：**用于表示一些不能显示出来的ASCII字符

现阶段我们常用的转义字符有：\n \\ \t

转义字符 含义 ASCII码值（十进制）
\a 警报 007
\b 退格(BS) ，将当前位置移到前一列 008
\f 换页(FF)，将当前位置移到下页开头 012
\n 换行(LF) ，将当前位置移到下一行开头 010
\r 回车(CR) ，将当前位置移到本行开头 013
\t 水平制表(HT) （跳到下一个TAB位置） 009
\v 垂直制表(VT) 011
\\ 代表一个反斜线字符"" 092
’ 代表一个单引号（撇号）字符 039
" 代表一个双引号字符 034
? 代表一个问号 063
\0 数字0 000
\ddd 8进制转义字符，d范围0~7 3位8进制
\xhh 16进制转义字符，h范围09，af，A~F 3位16进制

示例：

Escape Characters

Purpose: used to represent some ASCII characters that cannot be displayed

The escape characters we commonly use at this stage are: \n \\ \t

Escape Character Meaning ASCII Code (decimal)
\a Bell (alert) 007
\b Backspace (BS), moves the current position to the previous column 008
\f Form feed (FF), moves the current position to the beginning of the next page 012
\n Line feed (LF), moves the current position to the beginning of the next line 010
\r Carriage return (CR), moves the current position to the beginning of the current line 013
\t Horizontal tab (HT) (jump to the next TAB position) 009
\v Vertical tab (VT) 011
\\ Represents a backslash character "" 092
’ Represents a single quote (apostrophe) character 039
" Represents a double quote character 034
? Represents a question mark 063
\0 The digit 0 000
\ddd Octal escape character, d ranges from 0 to 7 3-digit octal
\xhh Hexadecimal escape character, h ranges from 0-9, a-f, A-F 3-digit hexadecimal

Example:

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int main() {
	
	
	cout << "\\" << endl;
	cout << "\tHello" << endl;
	cout << "\n" << endl;

	system("pause");

	return 0;
}

字符串型

作用：用于表示一串字符

两种风格

  1. C风格字符串： char 变量名[] = "字符串值"

    示例：

String Type

Purpose: used to represent a string of characters

Two styles

  1. C-style string: char variableName[] = "string value"

    Example:

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int main() {

	char str1[] = "hello world";
	cout << str1 << endl;
    
	system("pause");

	return 0;
}

注意：C风格的字符串要用双引号括起来

  1. C++风格字符串： string 变量名 = "字符串值"

    示例：

Note: C-style strings must be enclosed in double quotes

  1. C+±style string: string variableName = "string value"

    Example:

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int main() {

	string str = "hello world";
	cout << str << endl;
	
	system("pause");

	return 0;
}

注意：C++风格字符串，需要加入头文件==#include<string>==

Note: C+±style strings require the header file #include<string>

布尔类型 bool

**作用：**布尔数据类型代表真或假的值

bool类型只有两个值：

  • true — 真（本质是1）
  • false — 假（本质是0）

bool类型占1个字节大小

示例：

Boolean Type bool

Purpose: the boolean data type represents a true or false value

The bool type has only two values:

  • true — true (essentially 1)
  • false — false (essentially 0)

The bool type occupies 1 byte

Example:

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int main() {

	bool flag = true;
	cout << flag << endl; // 1

	flag = false;
	cout << flag << endl; // 0

	cout << "size of bool = " << sizeof(bool) << endl; //1
	
	system("pause");

	return 0;
}

数据的输入

作用：用于从键盘获取数据

**关键字：**cin

语法： cin >> 变量

示例：

Data Input

Purpose: used to get data from the keyboard

Keyword: cin

Syntax: cin >> variable

Example:

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int main(){

	//整型输入
	int a = 0;
	cout << "请输入整型变量：" << endl;
	cin >> a;
	cout << a << endl;

	//浮点型输入
	double d = 0;
	cout << "请输入浮点型变量：" << endl;
	cin >> d;
	cout << d << endl;

	//字符型输入
	char ch = 0;
	cout << "请输入字符型变量：" << endl;
	cin >> ch;
	cout << ch << endl;

	//字符串型输入
	string str;
	cout << "请输入字符串型变量：" << endl;
	cin >> str;
	cout << str << endl;

	//布尔类型输入
	bool flag = true;
	cout << "请输入布尔型变量：" << endl;
	cin >> flag;
	cout << flag << endl;
	system("pause");
	return EXIT_SUCCESS;
}

运算符

**作用：**用于执行代码的运算

本章我们主要讲解以下几类运算符：

运算符类型 作用
算术运算符 用于处理四则运算
赋值运算符 用于将表达式的值赋给变量
比较运算符 用于表达式的比较，并返回一个真值或假值
逻辑运算符 用于根据表达式的值返回真值或假值

Operators

Purpose: used to perform operations on code

In this chapter we mainly explain the following types of operators:

Operator Type Purpose
Arithmetic operators Used to handle the four basic arithmetic operations
Assignment operators Used to assign the value of an expression to a variable
Comparison operators Used to compare expressions and return a true or false value
Logical operators Used to return a true or false value based on the value of an expression

算术运算符

作用：用于处理四则运算

算术运算符包括以下符号：

运算符 术语 示例 结果
+ 正号 +3 3
- 负号 -3 -3
+ 加 10 + 5 15
- 减 10 - 5 5
* 乘 10 * 5 50
/ 除 10 / 5 2
% 取模(取余) 10 % 3 1
++ 前置递增 a=2; b=++a; a=3; b=3;
++ 后置递增 a=2; b=a++; a=3; b=2;
– 前置递减 a=2; b=–a; a=1; b=1;
– 后置递减 a=2; b=a–; a=1; b=2;

示例1：

Arithmetic Operators

Purpose: used to handle the four basic arithmetic operations

Arithmetic operators include the following symbols:

Operator Term Example Result
+ Positive sign +3 3
- Negative sign -3 -3
+ Addition 10 + 5 15
- Subtraction 10 - 5 5
* Multiplication 10 * 5 50
/ Division 10 / 5 2
% Modulo (remainder) 10 % 3 1
++ Pre-increment a=2; b=++a; a=3; b=3;
++ Post-increment a=2; b=a++; a=3; b=2;
– Pre-decrement a=2; b=–a; a=1; b=1;
– Post-decrement a=2; b=a–; a=1; b=2;

Example 1:

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//加减乘除
int main() {

	int a1 = 10;
	int b1 = 3;

	cout << a1 + b1 << endl;
	cout << a1 - b1 << endl;
	cout << a1 * b1 << endl;
	cout << a1 / b1 << endl;  //两个整数相除结果依然是整数

	int a2 = 10;
	int b2 = 20;
	cout << a2 / b2 << endl; 

	int a3 = 10;
	int b3 = 0;
	//cout << a3 / b3 << endl; //报错，除数不可以为0


	//两个小数可以相除
	double d1 = 0.5;
	double d2 = 0.25;
	cout << d1 / d2 << endl;

	system("pause");

	return 0;
}

总结：在除法运算中，除数不能为0

示例2：

Summary: in division, the divisor cannot be 0

Example 2:

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//取模
int main() {

	int a1 = 10;
	int b1 = 3;

	cout << 10 % 3 << endl;

	int a2 = 10;
	int b2 = 20;

	cout << a2 % b2 << endl;

	int a3 = 10;
	int b3 = 0;

	//cout << a3 % b3 << endl; //取模运算时，除数也不能为0

	//两个小数不可以取模
	double d1 = 3.14;
	double d2 = 1.1;

	//cout << d1 % d2 << endl;

	system("pause");

	return 0;
}

总结：只有整型变量可以进行取模运算

示例3：

Summary: only integer variables can perform the modulo operation

Example 3:

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//递增
int main() {

	//后置递增
	int a = 10;
	a++; //等价于a = a + 1
	cout << a << endl; // 11

	//前置递增
	int b = 10;
	++b;
	cout << b << endl; // 11

	//区别
	//前置递增先对变量进行++，再计算表达式
	int a2 = 10;
	int b2 = ++a2 * 10;
	cout << b2 << endl;

	//后置递增先计算表达式，后对变量进行++
	int a3 = 10;
	int b3 = a3++ * 10;
	cout << b3 << endl;

	system("pause");

	return 0;
}

总结：前置递增先对变量进行++，再计算表达式，后置递增相反

Summary: pre-increment performs ++ on the variable first, then evaluates the expression; post-increment is the opposite

赋值运算符

**作用：**用于将表达式的值赋给变量

赋值运算符包括以下几个符号：

运算符 术语 示例 结果
= 赋值 a=2; b=3; a=2; b=3;
+= 加等于 a=0; a+=2; a=2;
-= 减等于 a=5; a-=3; a=2;
*= 乘等于 a=2; a*=2; a=4;
/= 除等于 a=4; a/=2; a=2;
%= 模等于 a=3; a%2; a=1;

示例：

Assignment Operators

Purpose: used to assign the value of an expression to a variable

Assignment operators include the following symbols:

Operator Term Example Result
= Assign a=2; b=3; a=2; b=3;
+= Add and assign a=0; a+=2; a=2;
-= Subtract and assign a=5; a-=3; a=2;
*= Multiply and assign a=2; a*=2; a=4;
/= Divide and assign a=4; a/=2; a=2;
%= Modulo and assign a=3; a%2; a=1;

Example:

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int main() {

	//赋值运算符

	// =
	int a = 10;
	a = 100;
	cout << "a = " << a << endl;

	// +=
	a = 10;
	a += 2; // a = a + 2;
	cout << "a = " << a << endl;

	// -=
	a = 10;
	a -= 2; // a = a - 2
	cout << "a = " << a << endl;

	// *=
	a = 10;
	a *= 2; // a = a * 2
	cout << "a = " << a << endl;

	// /=
	a = 10;
	a /= 2;  // a = a / 2;
	cout << "a = " << a << endl;

	// %=
	a = 10;
	a %= 2;  // a = a % 2;
	cout << "a = " << a << endl;

	system("pause");

	return 0;
}

比较运算符

**作用：**用于表达式的比较，并返回一个真值或假值

比较运算符有以下符号：

运算符 术语 示例 结果
== 相等于 4 == 3 0
!= 不等于 4 != 3 1
< 小于 4 < 3 0
> 大于 4 > 3 1
<= 小于等于 4 <= 3 0
>= 大于等于 4 >= 1 1

示例：

Comparison Operators

Purpose: used to compare expressions and return a true or false value

Comparison operators include the following symbols:

Operator Term Example Result
== Equal to 4 == 3 0
!= Not equal to 4 != 3 1
< Less than 4 < 3 0
> Greater than 4 > 3 1
<= Less than or equal to 4 <= 3 0
>= Greater than or equal to 4 >= 1 1

Example:

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int main() {

	int a = 10;
	int b = 20;

	cout << (a == b) << endl; // 0 

	cout << (a != b) << endl; // 1

	cout << (a > b) << endl; // 0

	cout << (a < b) << endl; // 1

	cout << (a >= b) << endl; // 0

	cout << (a <= b) << endl; // 1
	
	system("pause");

	return 0;
}

注意：C和C++ 语言的比较运算中， “真”用数字“1”来表示， “假”用数字“0”来表示。

Note: in comparison operations in C and C++, “true” is represented by the number “1” and “false” by the number “0”.

逻辑运算符

**作用：**用于根据表达式的值返回真值或假值

逻辑运算符有以下符号：

运算符 术语 示例 结果
! 非 !a 如果a为假，则!a为真； 如果a为真，则!a为假。
&& 与 a && b 如果a和b都为真，则结果为真，否则为假。
|| 或 a || b 如果a和b有一个为真，则结果为真，二者都为假时，结果为假。

**示例1：**逻辑非

Logical Operators

Purpose: used to return a true or false value based on the value of an expression

Logical operators include the following symbols:

Operator Term Example Result
! NOT !a If a is false, !a is true; if a is true, !a is false.
&& AND a && b If both a and b are true, the result is true; otherwise it is false.
|| OR a || b If either a or b is true, the result is true; when both are false, the result is false.

Example 1: Logical NOT

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//逻辑运算符  --- 非
int main() {

	int a = 10;

	cout << !a << endl; // 0

	cout << !!a << endl; // 1

	system("pause");

	return 0;
}

总结： 真变假，假变真

**示例2：**逻辑与

Summary: true becomes false, false becomes true

Example 2: Logical AND

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//逻辑运算符  --- 与
int main() {

	int a = 10;
	int b = 10;

	cout << (a && b) << endl;// 1

	a = 10;
	b = 0;

	cout << (a && b) << endl;// 0 

	a = 0;
	b = 0;

	cout << (a && b) << endl;// 0

	system("pause");

	return 0;
}

总结：逻辑与运算符总结： 同真为真，其余为假

**示例3：**逻辑或

Summary of the logical AND operator: true only when both are true; false otherwise

Example 3: Logical OR

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//逻辑运算符  --- 或
int main() {

	int a = 10;
	int b = 10;

	cout << (a || b) << endl;// 1

	a = 10;
	b = 0;

	cout << (a || b) << endl;// 1 

	a = 0;
	b = 0;

	cout << (a || b) << endl;// 0

	system("pause");

	return 0;
}

逻辑或运算符总结： 同假为假，其余为真

Summary of the logical OR operator: false only when both are false; true otherwise

程序流程结构

C/C++支持最基本的三种程序运行结构：顺序结构、选择结构、循环结构

  • 顺序结构：程序按顺序执行，不发生跳转
  • 选择结构：依据条件是否满足，有选择的执行相应功能
  • 循环结构：依据条件是否满足，循环多次执行某段代码

Program Flow Control

C/C++ supports three basic program execution structures: sequential structure, selection structure, and loop structure

  • Sequential structure: the program executes in order without jumps
  • Selection structure: based on whether the condition is satisfied, the corresponding function is selectively executed
  • Loop structure: based on whether the condition is satisfied, a piece of code is executed repeatedly

4.1 选择结构

if语句

**作用：**执行满足条件的语句

if语句的三种形式

  • 单行格式if语句

  • 多行格式if语句

  • 多条件的if语句

  1. 单行格式if语句：if(条件){ 条件满足执行的语句 }

    img

    示例：

4.1 Selection Structure

if Statement

Purpose: executes the statements that satisfy a condition

The three forms of the if statement

  • Single-line if statement

  • Multi-line if statement

  • Multi-condition if statement

  1. Single-line if statement: if(condition){ statement executed when the condition is satisfied }

    img

    Example:

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int main() {

	//选择结构-单行if语句
	//输入一个分数，如果分数大于600分，视为考上一本大学，并在屏幕上打印

	int score = 0;
	cout << "请输入一个分数：" << endl;
	cin >> score;

	cout << "您输入的分数为： " << score << endl;

	//if语句
	//注意事项，在if判断语句后面，不要加分号
	if (score > 600)
	{
		cout << "我考上了一本大学！！！" << endl;
	}

	system("pause");

	return 0;
}

注意：if条件表达式后不要加分号

  1. 多行格式if语句：if(条件){ 条件满足执行的语句 }else{ 条件不满足执行的语句 };

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示例：

Note: do not add a semicolon after the if condition expression

  1. Multi-line if statement: if(condition){ statement executed when the condition is satisfied }else{ statement executed when the condition is not satisfied };

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Example:

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int main() {

	int score = 0;

	cout << "请输入考试分数：" << endl;

	cin >> score;

	if (score > 600)
	{
		cout << "我考上了一本大学" << endl;
	}
	else
	{
		cout << "我未考上一本大学" << endl;
	}

	system("pause");

	return 0;
}
  1. 多条件的if语句：if(条件1){ 条件1满足执行的语句 }else if(条件2){条件2满足执行的语句}... else{ 都不满足执行的语句}

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示例：

  1. Multi-condition if statement: if(condition 1){ statement executed when condition 1 is satisfied }else if(condition 2){ statement executed when condition 2 is satisfied }... else{ statement executed when none is satisfied }

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Example:

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	int main() {

	int score = 0;

	cout << "请输入考试分数：" << endl;

	cin >> score;

	if (score > 600)
	{
		cout << "我考上了一本大学" << endl;
	}
	else if (score > 500)
	{
		cout << "我考上了二本大学" << endl;
	}
	else if (score > 400)
	{
		cout << "我考上了三本大学" << endl;
	}
	else
	{
		cout << "我未考上本科" << endl;
	}

	system("pause");

	return 0;
}

嵌套if语句：在if语句中，可以嵌套使用if语句，达到更精确的条件判断

案例需求：

  • 提示用户输入一个高考考试分数，根据分数做如下判断
  • 分数如果大于600分视为考上一本，大于500分考上二本，大于400考上三本，其余视为未考上本科；
  • 在一本分数中，如果大于700分，考入北大，大于650分，考入清华，大于600考入人大。

示例：

Nested if statements: inside an if statement, you can nest another if statement to achieve more precise condition checking

Case requirements:

  • Prompt the user to enter a college entrance exam score and make the following judgments based on the score
  • A score greater than 600 is considered admitted to a first-tier university, greater than 500 to a second-tier university, greater than 400 to a third-tier university, otherwise considered not admitted to any undergraduate university;
  • For scores in the first-tier range, a score greater than 700 means admitted to Peking University, greater than 650 means admitted to Tsinghua University, greater than 600 means admitted to Renmin University.

Example:

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int main() {

	int score = 0;

	cout << "请输入考试分数：" << endl;

	cin >> score;

	if (score > 600)
	{
		cout << "我考上了一本大学" << endl;
		if (score > 700)
		{
			cout << "我考上了北大" << endl;
		}
		else if (score > 650)
		{
			cout << "我考上了清华" << endl;
		}
		else
		{
			cout << "我考上了人大" << endl;
		}
		
	}
	else if (score > 500)
	{
		cout << "我考上了二本大学" << endl;
	}
	else if (score > 400)
	{
		cout << "我考上了三本大学" << endl;
	}
	else
	{
		cout << "我未考上本科" << endl;
	}

	system("pause");

	return 0;
}

练习案例： 三只小猪称体重

有三只小猪ABC，请分别输入三只小猪的体重，并且判断哪只小猪最重？三只小猪

Practice case: Three little pigs weigh themselves

There are three little pigs, A, B, and C. Please enter the weight of each pig and determine which one is the heaviest?三只小猪

三目运算符

作用： 通过三目运算符实现简单的判断

语法：表达式1 ? 表达式2 ：表达式3

解释：

如果表达式1的值为真，执行表达式2，并返回表达式2的结果；

如果表达式1的值为假，执行表达式3，并返回表达式3的结果。

示例：

Ternary Operator

Purpose: implement simple judgments through the ternary operator

Syntax: expression1 ? expression2 : expression3

Explanation:

If the value of expression1 is true, expression2 is executed and its result is returned;

If the value of expression1 is false, expression3 is executed and its result is returned.

Example:

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int main() {

	int a = 10;
	int b = 20;
	int c = 0;

	c = a > b ? a : b;
	cout << "c = " << c << endl;

	//C++中三目运算符返回的是变量,可以继续赋值

	(a > b ? a : b) = 100;

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

	system("pause");

	return 0;
}

总结：和if语句比较，三目运算符优点是短小整洁，缺点是如果用嵌套，结构不清晰

Summary: compared with the if statement, the advantage of the ternary operator is that it is short and tidy; the disadvantage is that if nested, the structure is not clear

switch语句

**作用：**执行多条件分支语句

语法：

switch Statement

Purpose: executes multi-condition branch statements

Syntax:

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switch(表达式)

{

	case 结果1：执行语句;break;

	case 结果2：执行语句;break;

	...

	default:执行语句;break;

}

示例：

Example:

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int main() {

	//请给电影评分 
	//10 ~ 9   经典   
	// 8 ~ 7   非常好
	// 6 ~ 5   一般
	// 5分以下 烂片

	int score = 0;
	cout << "请给电影打分" << endl;
	cin >> score;

	switch (score)
	{
	case 10:
	case 9:
		cout << "经典" << endl;
		break;
	case 8:
		cout << "非常好" << endl;
		break;
	case 7:
	case 6:
		cout << "一般" << endl;
		break;
	default:
		cout << "烂片" << endl;
		break;
	}

	system("pause");

	return 0;
}

注意1：switch语句中表达式类型只能是整型或者字符型

注意2：case里如果没有break，那么程序会一直向下执行

总结：与if语句比，对于多条件判断时，switch的结构清晰，执行效率高，缺点是switch不可以判断区间

Note 1: the expression type in a switch statement can only be integer or character

Note 2: if there is no break in a case, the program will continue to execute downward

Summary: compared with the if statement, for multi-condition judgments, the switch structure is clear and executes efficiently; the disadvantage is that switch cannot judge ranges

循环结构

while循环语句

**作用：**满足循环条件，执行循环语句

语法：while(循环条件){ 循环语句 }

解释：只要循环条件的结果为真，就执行循环语句

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示例：

Loop Structures

while Loop Statement

Purpose: while the loop condition is satisfied, execute the loop statements

Syntax: while(loop condition){ loop statements }

Explanation: as long as the result of the loop condition is true, the loop statements are executed

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Example:

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int main() {

	int num = 0;
	while (num < 10)
	{
		cout << "num = " << num << endl;
		num++;
	}
	
	system("pause");

	return 0;
}

注意：在执行循环语句时候，程序必须提供跳出循环的出口，否则出现死循环

while循环练习案例：猜数字

**案例描述：**系统随机生成一个1到100之间的数字，玩家进行猜测，如果猜错，提示玩家数字过大或过小，如果猜对恭喜玩家胜利，并且退出游戏。

猜数字

Note: when executing loop statements, the program must provide an exit to break out of the loop, otherwise an infinite loop will occur

while loop practice case: Guess the number

Case description: the system randomly generates a number between 1 and 100, and the player guesses it. If the guess is wrong, prompt the player that the number is too large or too small. If the guess is correct, congratulate the player on winning and exit the game.

猜数字

do…while循环语句

作用： 满足循环条件，执行循环语句

语法： do{ 循环语句 } while(循环条件);

**注意：**与while的区别在于do…while会先执行一次循环语句，再判断循环条件

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示例：

do…while Loop Statement

Purpose: while the loop condition is satisfied, execute the loop statements

Syntax: do{ loop statements } while(loop condition);

Note: the difference from while is that do…while executes the loop statements once first, then checks the loop condition

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Example:

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int main() {

	int num = 0;

	do
	{
		cout << num << endl;
		num++;

	} while (num < 10);
	
	
	system("pause");

	return 0;
}

总结：与while循环区别在于，do…while先执行一次循环语句，再判断循环条件

练习案例：水仙花数

**案例描述：**水仙花数是指一个 3 位数，它的每个位上的数字的 3次幂之和等于它本身

例如：1^3 + 5^3+ 3^3 = 153

请利用do…while语句，求出所有3位数中的水仙花数

Summary: the difference from the while loop is that do…while executes the loop statements once first, then checks the loop condition

Practice case: Narcissistic numbers

Case description: a narcissistic number is a 3-digit number whose sum of the cubes of each digit equals itself

For example: 1^3 + 5^3+ 3^3 = 153

Please use the do…while statement to find all narcissistic numbers among 3-digit numbers

for循环语句

作用： 满足循环条件，执行循环语句

语法：for(起始表达式;条件表达式;末尾循环体) { 循环语句; }

示例：

for Loop Statement

Purpose: while the loop condition is satisfied, execute the loop statements

Syntax: for(start expression;condition expression;end-of-loop body) { loop statements; }

Example:

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int main() {

	for (int i = 0; i < 10; i++)
	{
		cout << i << endl;
	}
	
	system("pause");

	return 0;
}

详解：

1541673704101

注意：for循环中的表达式，要用分号进行分隔

总结：while , do…while, for都是开发中常用的循环语句，for循环结构比较清晰，比较常用

练习案例：敲桌子

案例描述：从1开始数到数字100， 如果数字个位含有7，或者数字十位含有7，或者该数字是7的倍数，我们打印敲桌子，其余数字直接打印输出。

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Detailed explanation:

1541673704101

Note: the expressions in a for loop must be separated by semicolons

Summary: while, do…while, and for are all commonly used loop statements in development. The for loop has a clearer structure and is the most commonly used

Practice case: Knock the table

Case description: count from 1 to 100. If the digit in the ones place contains 7, or the digit in the tens place contains 7, or the number is a multiple of 7, we print “knock the table”; otherwise, print the number directly.

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嵌套循环

作用： 在循环体中再嵌套一层循环，解决一些实际问题

例如我们想在屏幕中打印如下图片，就需要利用嵌套循环

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示例：

Nested Loops

Purpose: nest another layer of loop inside the loop body to solve some practical problems

For example, if we want to print the following image on the screen, we need to use nested loops

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Example:

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int main() {

	//外层循环执行1次，内层循环执行1轮
	for (int i = 0; i < 10; i++)
	{
		for (int j = 0; j < 10; j++)
		{
			cout << "*" << " ";
		}
		cout << endl;
	}

	system("pause");

	return 0;
}

**练习案例：**乘法口诀表

案例描述：利用嵌套循环，实现九九乘法表

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Practice case: Multiplication table

Case description: use nested loops to implement the 9x9 multiplication table

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跳转语句

break语句

作用: 用于跳出选择结构或者循环结构

break使用的时机：

  • 出现在switch条件语句中，作用是终止case并跳出switch
  • 出现在循环语句中，作用是跳出当前的循环语句
  • 出现在嵌套循环中，跳出最近的内层循环语句

示例1：

Jump Statements

break Statement

Purpose: used to break out of selection structures or loop structures

When to use break:

  • In a switch condition statement, it terminates the case and breaks out of the switch
  • In a loop statement, it breaks out of the current loop
  • In nested loops, it breaks out of the nearest inner loop

Example 1:

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int main() {
	//1、在switch 语句中使用break
	cout << "请选择您挑战副本的难度：" << endl;
	cout << "1、普通" << endl;
	cout << "2、中等" << endl;
	cout << "3、困难" << endl;

	int num = 0;

	cin >> num;

	switch (num)
	{
	case 1:
		cout << "您选择的是普通难度" << endl;
		break;
	case 2:
		cout << "您选择的是中等难度" << endl;
		break;
	case 3:
		cout << "您选择的是困难难度" << endl;
		break;
	}

	system("pause");

	return 0;
}

示例2：

Example 2:

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int main() {
	//2、在循环语句中用break
	for (int i = 0; i < 10; i++)
	{
		if (i == 5)
		{
			break; //跳出循环语句
		}
		cout << i << endl;
	}

	system("pause");

	return 0;
}

示例3：

Example 3:

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int main() {
	//在嵌套循环语句中使用break，退出内层循环
	for (int i = 0; i < 10; i++)
	{
		for (int j = 0; j < 10; j++)
		{
			if (j == 5)
			{
				break;
			}
			cout << "*" << " ";
		}
		cout << endl;
	}
	
	system("pause");

	return 0;
}

continue语句

**作用：**在循环语句中，跳过本次循环中余下尚未执行的语句，继续执行下一次循环

示例：

continue Statement

Purpose: in a loop statement, skip the remaining unexecuted statements in the current iteration and continue with the next iteration

Example:

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int main() {

	for (int i = 0; i < 100; i++)
	{
		if (i % 2 == 0)
		{
			continue;
		}
		cout << i << endl;
	}
	
	system("pause");

	return 0;
}

注意：continue并没有使整个循环终止，而break会跳出循环

Note: continue does not terminate the entire loop, while break breaks out of the loop

goto语句

**作用：**可以无条件跳转语句

语法： goto 标记;

**解释：**如果标记的名称存在，执行到goto语句时，会跳转到标记的位置

示例：

goto Statement

Purpose: can unconditionally jump to a statement

Syntax: goto label;

Explanation: if the label exists, when the goto statement is executed, the program jumps to the position of the label

Example:

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int main() {

	cout << "1" << endl;

	goto FLAG;

	cout << "2" << endl;
	cout << "3" << endl;
	cout << "4" << endl;

	FLAG:

	cout << "5" << endl;
	
	system("pause");

	return 0;
}

注意：在程序中不建议使用goto语句，以免造成程序流程混乱

Note: it is not recommended to use the goto statement in programs, to avoid confusing the program flow

数组

概述

所谓数组，就是一个集合，里面存放了相同类型的数据元素

**特点1：**数组中的每个数据元素都是相同的数据类型

**特点2：**数组是由连续的内存位置组成的

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Arrays

Overview

An array is a collection that stores data elements of the same type

Feature 1: every data element in an array is of the same data type

Feature 2: an array is composed of contiguous memory locations

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一维数组

一维数组定义方式

一维数组定义的三种方式：

  1. 数据类型 数组名[ 数组长度 ];
  2. 数据类型 数组名[ 数组长度 ] = { 值1，值2 ...};
  3. 数据类型 数组名[ ] = { 值1，值2 ...};

示例

One-Dimensional Arrays

Ways to Define a One-Dimensional Array

There are three ways to define a one-dimensional array:

  1. data type array name[ array length ];
  2. data type array name[ array length ] = { value 1, value 2 ...};
  3. data type array name[ ] = { value 1, value 2 ...};

Example

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int main() {

	//定义方式1
	//数据类型 数组名[元素个数];
	int score[10];

	//利用下标赋值
	score[0] = 100;
	score[1] = 99;
	score[2] = 85;

	//利用下标输出
	cout << score[0] << endl;
	cout << score[1] << endl;
	cout << score[2] << endl;


	//第二种定义方式
	//数据类型 数组名[元素个数] =  {值1，值2 ，值3 ...};
	//如果{}内不足10个数据，剩余数据用0补全
	int score2[10] = { 100, 90,80,70,60,50,40,30,20,10 };
	
	//逐个输出
	//cout << score2[0] << endl;
	//cout << score2[1] << endl;

	//一个一个输出太麻烦，因此可以利用循环进行输出
	for (int i = 0; i < 10; i++)
	{
		cout << score2[i] << endl;
	}

	//定义方式3
	//数据类型 数组名[] =  {值1，值2 ，值3 ...};
	int score3[] = { 100,90,80,70,60,50,40,30,20,10 };

	for (int i = 0; i < 10; i++)
	{
		cout << score3[i] << endl;
	}

	system("pause");

	return 0;
}

总结1：数组名的命名规范与变量名命名规范一致，不要和变量重名

总结2：数组中下标是从0开始索引

Summary 1: the naming rules for array names are the same as those for variable names; do not use the same name as a variable

Summary 2: indices in an array start from 0

一维数组数组名

一维数组名称的用途：

  1. 可以统计整个数组在内存中的长度
  2. 可以获取数组在内存中的首地址

示例：

The Array Name of a One-Dimensional Array

The purposes of a one-dimensional array name:

  1. It can calculate the length of the entire array in memory
  2. It can get the first address of the array in memory

Example:

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int main() {

	//数组名用途
	//1、可以获取整个数组占用内存空间大小
	int arr[10] = { 1,2,3,4,5,6,7,8,9,10 };

	cout << "整个数组所占内存空间为： " << sizeof(arr) << endl;
	cout << "每个元素所占内存空间为： " << sizeof(arr[0]) << endl;
	cout << "数组的元素个数为： " << sizeof(arr) / sizeof(arr[0]) << endl;

	//2、可以通过数组名获取到数组首地址
	cout << "数组首地址为： " << (int)arr << endl;
	cout << "数组中第一个元素地址为： " << (int)&arr[0] << endl;
	cout << "数组中第二个元素地址为： " << (int)&arr[1] << endl;

	//arr = 100; 错误，数组名是常量，因此不可以赋值


	system("pause");

	return 0;
}

注意：数组名是常量，不可以赋值

总结1：直接打印数组名，可以查看数组所占内存的首地址

总结2：对数组名进行sizeof，可以获取整个数组占内存空间的大小

练习案例1：五只小猪称体重

案例描述：

在一个数组中记录了五只小猪的体重，如：int arr[5] = {300,350,200,400,250};

找出并打印最重的小猪体重。

**练习案例2：**数组元素逆置

**案例描述：**请声明一个5个元素的数组，并且将元素逆置.

(如原数组元素为：1,3,2,5,4;逆置后输出结果为:4,5,2,3,1);

Note: the array name is a constant and cannot be assigned

Summary 1: printing the array name directly shows the first address of the memory occupied by the array

Summary 2: using sizeof on the array name gives the size of the memory occupied by the entire array

Practice case 1: Five little pigs weigh themselves

Case description:

The weights of five little pigs are recorded in an array, such as: int arr[5] = {300,350,200,400,250};

Find and print the weight of the heaviest little pig.

Practice case 2: Reversing array elements

Case description: declare an array of 5 elements and reverse the elements.

(If the original array elements are: 1,3,2,5,4; after reversing, the output result is: 4,5,2,3,1);

冒泡排序

作用： 最常用的排序算法，对数组内元素进行排序

  1. 比较相邻的元素。如果第一个比第二个大，就交换他们两个。
  2. 对每一对相邻元素做同样的工作，执行完毕后，找到第一个最大值。
  3. 重复以上的步骤，每次比较次数-1，直到不需要比较

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示例： 将数组 { 4,2,8,0,5,7,1,3,9 } 进行升序排序

Bubble Sort

Purpose: the most commonly used sorting algorithm, used to sort the elements in an array

  1. Compare adjacent elements. If the first is greater than the second, swap them.
  2. Do the same work for each pair of adjacent elements; after finishing, find the first maximum value.
  3. Repeat the above steps, reducing the number of comparisons by 1 each time, until no more comparisons are needed

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Example: sort the array { 4,2,8,0,5,7,1,3,9 } in ascending order

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int main() {

	int arr[9] = { 4,2,8,0,5,7,1,3,9 };

	for (int i = 0; i < 9 - 1; i++)
	{
		for (int j = 0; j < 9 - 1 - i; j++)
		{
			if (arr[j] > arr[j + 1])
			{
				int temp = arr[j];
				arr[j] = arr[j + 1];
				arr[j + 1] = temp;
			}
		}
	}

	for (int i = 0; i < 9; i++)
	{
		cout << arr[i] << endl;
	}
    
	system("pause");

	return 0;
}

二维数组

二维数组就是在一维数组上，多加一个维度。

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二维数组定义方式

二维数组定义的四种方式：

  1. 数据类型 数组名[ 行数 ][ 列数 ];
  2. 数据类型 数组名[ 行数 ][ 列数 ] = { {数据1，数据2 } ，{数据3，数据4 } };
  3. 数据类型 数组名[ 行数 ][ 列数 ] = { 数据1，数据2，数据3，数据4};
  4. 数据类型 数组名[ ][ 列数 ] = { 数据1，数据2，数据3，数据4};

建议：以上4种定义方式，利用第二种更加直观，提高代码的可读性

示例：

Two-Dimensional Arrays

A two-dimensional array adds one more dimension on top of a one-dimensional array.

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Ways to Define a Two-Dimensional Array

There are four ways to define a two-dimensional array:

  1. data type array name[ rows ][ columns ];
  2. data type array name[ rows ][ columns ] = { {data 1, data 2 } ，{data 3, data 4 } };
  3. data type array name[ rows ][ columns ] = { data 1, data 2, data 3, data 4};
  4. data type array name[ ][ columns ] = { data 1, data 2, data 3, data 4};

Suggestion: among the above 4 definition methods, the second one is more intuitive and improves code readability

Example:

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int main() {

	//方式1  
	//数组类型 数组名 [行数][列数]
	int arr[2][3];
	arr[0][0] = 1;
	arr[0][1] = 2;
	arr[0][2] = 3;
	arr[1][0] = 4;
	arr[1][1] = 5;
	arr[1][2] = 6;

	for (int i = 0; i < 2; i++)
	{
		for (int j = 0; j < 3; j++)
		{
			cout << arr[i][j] << " ";
		}
		cout << endl;
	}

	//方式2 
	//数据类型 数组名[行数][列数] = { {数据1，数据2 } ，{数据3，数据4 } };
	int arr2[2][3] =
	{
		{1,2,3},
		{4,5,6}
	};

	//方式3
	//数据类型 数组名[行数][列数] = { 数据1，数据2 ,数据3，数据4  };
	int arr3[2][3] = { 1,2,3,4,5,6 }; 

	//方式4 
	//数据类型 数组名[][列数] = { 数据1，数据2 ,数据3，数据4  };
	int arr4[][3] = { 1,2,3,4,5,6 };
	
	system("pause");

	return 0;
}

总结：在定义二维数组时，如果初始化了数据，可以省略行数

Summary: when defining a two-dimensional array, if the data is initialized, the number of rows can be omitted

二维数组数组名

  • 查看二维数组所占内存空间
  • 获取二维数组首地址

示例：

The Array Name of a Two-Dimensional Array

  • View the memory space occupied by a two-dimensional array
  • Get the first address of a two-dimensional array

Example:

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int main() {

	//二维数组数组名
	int arr[2][3] =
	{
		{1,2,3},
		{4,5,6}
	};

	cout << "二维数组大小： " << sizeof(arr) << endl;
	cout << "二维数组一行大小： " << sizeof(arr[0]) << endl;
	cout << "二维数组元素大小： " << sizeof(arr[0][0]) << endl;

	cout << "二维数组行数： " << sizeof(arr) / sizeof(arr[0]) << endl;
	cout << "二维数组列数： " << sizeof(arr[0]) / sizeof(arr[0][0]) << endl;

	//地址
	cout << "二维数组首地址：" << arr << endl;
	cout << "二维数组第一行地址：" << arr[0] << endl;
	cout << "二维数组第二行地址：" << arr[1] << endl;

	cout << "二维数组第一个元素地址：" << &arr[0][0] << endl;
	cout << "二维数组第二个元素地址：" << &arr[0][1] << endl;

	system("pause");

	return 0;
}

总结1：二维数组名就是这个数组的首地址

总结2：对二维数组名进行sizeof时，可以获取整个二维数组占用的内存空间大小

Summary 1: the name of a two-dimensional array is the first address of the array

Summary 2: using sizeof on a two-dimensional array name gives the size of the memory space occupied by the entire two-dimensional array

二维数组应用案例

考试成绩统计：

案例描述：有三名同学（张三，李四，王五），在一次考试中的成绩分别如下表，请分别输出三名同学的总成绩

语文 数学 英语
张三 100 100 100
李四 90 50 100
王五 60 70 80

参考答案：

Two-Dimensional Array Application Case

Exam score statistics:

Case description: there are three students (Zhang San, Li Si, Wang Wu), and their scores in an exam are shown in the table below. Please output the total score of each of the three students

Chinese Math English
Zhang San 100 100 100
Li Si 90 50 100
Wang Wu 60 70 80

Reference answer:

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int main() {

	int scores[3][3] =
	{
		{100,100,100},
		{90,50,100},
		{60,70,80},
	};

	string names[3] = { "张三","李四","王五" };

	for (int i = 0; i < 3; i++)
	{
		int sum = 0;
		for (int j = 0; j < 3; j++)
		{
			sum += scores[i][j];
		}
		cout << names[i] << "同学总成绩为： " << sum << endl;
	}

	system("pause");

	return 0;
}

函数

概述

**作用：**将一段经常使用的代码封装起来，减少重复代码

一个较大的程序，一般分为若干个程序块，每个模块实现特定的功能。

Functions

Overview

Purpose: encapsulate a piece of frequently used code to reduce duplicate code

A large program is generally divided into several program blocks, and each module implements a specific function.

函数的定义

函数的定义一般主要有5个步骤：

1、返回值类型

2、函数名

3、参数表列

4、函数体语句

5、return 表达式

语法：

Function Definition

A function definition generally involves 5 main steps:

  1. Return value type

  2. Function name

  3. Parameter list

  4. Function body statements

  5. return expression

Syntax:

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返回值类型 函数名 （参数列表）
{

       函数体语句

       return表达式

}
  • 返回值类型 ：一个函数可以返回一个值。在函数定义中
  • 函数名：给函数起个名称
  • 参数列表：使用该函数时，传入的数据
  • 函数体语句：花括号内的代码，函数内需要执行的语句
  • return表达式： 和返回值类型挂钩，函数执行完后，返回相应的数据

**示例：**定义一个加法函数，实现两个数相加

  • Return value type: a function can return a value. In the function definition
  • Function name: give the function a name
  • Parameter list: the data passed in when using the function
  • Function body statements: the code inside the curly braces, the statements that need to be executed inside the function
  • return expression: tied to the return value type, returns the corresponding data after the function finishes executing

Example: define an addition function to add two numbers

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//函数定义
int add(int num1, int num2)
{
	int sum = num1 + num2;
	return sum;
}

函数的调用

**功能：**使用定义好的函数

语法：函数名（参数）

示例：

Function Calls

Function: use a defined function

Syntax: function name(parameters)

Example:

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//函数定义
int add(int num1, int num2) //定义中的num1,num2称为形式参数，简称形参
{
	int sum = num1 + num2;
	return sum;
}

int main() {

	int a = 10;
	int b = 10;
	//调用add函数
	int sum = add(a, b);//调用时的a，b称为实际参数，简称实参
	cout << "sum = " << sum << endl;

	a = 100;
	b = 100;

	sum = add(a, b);
	cout << "sum = " << sum << endl;

	system("pause");

	return 0;
}

总结：函数定义里小括号内称为形参，函数调用时传入的参数称为实参

Summary: the parameters inside the parentheses in the function definition are called formal parameters, and the parameters passed in when calling the function are called actual parameters

值传递

  • 所谓值传递，就是函数调用时实参将数值传入给形参
  • 值传递时，如果形参发生，并不会影响实参

示例：

Pass by Value

  • The so-called pass by value means that when a function is called, the actual parameter passes its value to the formal parameter
  • With pass by value, if the formal parameter changes, it does not affect the actual parameter

Example:

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void swap(int num1, int num2)
{
	cout << "交换前：" << endl;
	cout << "num1 = " << num1 << endl;
	cout << "num2 = " << num2 << endl;

	int temp = num1;
	num1 = num2;
	num2 = temp;

	cout << "交换后：" << endl;
	cout << "num1 = " << num1 << endl;
	cout << "num2 = " << num2 << endl;

	//return ; 当函数声明时候，不需要返回值，可以不写return
}

int main() {

	int a = 10;
	int b = 20;

	swap(a, b);

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

	system("pause");

	return 0;
}

总结： 值传递时，形参是修饰不了实参的

Summary: with pass by value, the formal parameter cannot modify the actual parameter

函数的常见样式

常见的函数样式有4种

  1. 无参无返
  2. 有参无返
  3. 无参有返
  4. 有参有返

示例：

Common Function Styles

There are 4 common function styles

  1. No parameters, no return value
  2. With parameters, no return value
  3. No parameters, with return value
  4. With parameters, with return value

Example:

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//函数常见样式
//1、 无参无返
void test01()
{
	//void a = 10; //无类型不可以创建变量,原因无法分配内存
	cout << "this is test01" << endl;
	//test01(); 函数调用
}

//2、 有参无返
void test02(int a)
{
	cout << "this is test02" << endl;
	cout << "a = " << a << endl;
}

//3、无参有返
int test03()
{
	cout << "this is test03 " << endl;
	return 10;
}

//4、有参有返
int test04(int a, int b)
{
	cout << "this is test04 " << endl;
	int sum = a + b;
	return sum;
}

函数的声明

作用： 告诉编译器函数名称及如何调用函数。函数的实际主体可以单独定义。

  • 函数的声明可以多次，但是函数的定义只能有一次

示例：

Function Declaration

Purpose: tell the compiler the function name and how to call it. The actual body of the function can be defined separately.

  • A function can be declared multiple times, but its definition can only appear once

Example:

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//声明可以多次，定义只能一次
//声明
int max(int a, int b);
int max(int a, int b);
//定义
int max(int a, int b)
{
	return a > b ? a : b;
}

int main() {

	int a = 100;
	int b = 200;

	cout << max(a, b) << endl;

	system("pause");

	return 0;
}

函数的分文件编写

**作用：**让代码结构更加清晰

函数分文件编写一般有4个步骤

  1. 创建后缀名为.h的头文件
  2. 创建后缀名为.cpp的源文件
  3. 在头文件中写函数的声明
  4. 在源文件中写函数的定义

示例：

Writing Functions in Separate Files

Purpose: make the code structure clearer

Writing functions in separate files generally has 4 steps

  1. Create a header file with the suffix .h
  2. Create a source file with the suffix .cpp
  3. Write the function declaration in the header file
  4. Write the function definition in the source file

Example:

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//swap.h文件
#include<iostream>
using namespace std;

//实现两个数字交换的函数声明
void swap(int a, int b);

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//swap.cpp文件
#include "swap.h"

void swap(int a, int b)
{
	int temp = a;
	a = b;
	b = temp;

	cout << "a = " << a << endl;
	cout << "b = " << b << endl;
}
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//main函数文件
#include "swap.h"
int main() {

	int a = 100;
	int b = 200;
	swap(a, b);

	system("pause");

	return 0;
}

指针

指针的基本概念

指针的作用： 可以通过指针间接访问内存

  • 内存编号是从0开始记录的，一般用十六进制数字表示
  • 可以利用指针变量保存地址

Pointers

Basic Concepts of Pointers

The purpose of pointers: memory can be accessed indirectly through pointers

  • Memory numbers start from 0 and are generally represented in hexadecimal
  • Pointer variables can be used to store addresses

指针变量的定义和使用

指针变量定义语法： 数据类型 * 变量名；

示例：

Defining and Using Pointer Variables

Pointer variable definition syntax: data type * variable name;

Example:

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int main() {

	//1、指针的定义
	int a = 10; //定义整型变量a
	
	//指针定义语法： 数据类型 * 变量名 ;
	int * p;

	//指针变量赋值
	p = &a; //指针指向变量a的地址
	cout << &a << endl; //打印数据a的地址
	cout << p << endl;  //打印指针变量p

	//2、指针的使用
	//通过*操作指针变量指向的内存
	cout << "*p = " << *p << endl;

	system("pause");

	return 0;
}

指针变量和普通变量的区别

  • 普通变量存放的是数据,指针变量存放的是地址
  • 指针变量可以通过" * "操作符，操作指针变量指向的内存空间，这个过程称为解引用

总结1： 我们可以通过 & 符号 获取变量的地址

总结2：利用指针可以记录地址

总结3：对指针变量解引用，可以操作指针指向的内存

The difference between pointer variables and ordinary variables

  • Ordinary variables store data, while pointer variables store addresses
  • A pointer variable can use the “*” operator to operate on the memory space it points to; this process is called dereferencing

Summary 1: we can get the address of a variable through the & symbol

Summary 2: pointers can be used to record addresses

Summary 3: dereferencing a pointer variable allows us to operate on the memory it points to

指针所占内存空间

提问：指针也是种数据类型，那么这种数据类型占用多少内存空间？

示例：

Memory Space Occupied by Pointers

Question: a pointer is also a data type, so how much memory space does this data type occupy?

Example:

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int main() {

	int a = 10;

	int * p;
	p = &a; //指针指向数据a的地址

	cout << *p << endl; //* 解引用
	cout << sizeof(p) << endl;
	cout << sizeof(char *) << endl;
	cout << sizeof(float *) << endl;
	cout << sizeof(double *) << endl;

	system("pause");

	return 0;
}

总结：所有指针类型在32位操作系统下是4个字节

Summary: all pointer types occupy 4 bytes on 32-bit operating systems

空指针和野指针

空指针：指针变量指向内存中编号为0的空间

**用途：**初始化指针变量

**注意：**空指针指向的内存是不可以访问的

示例1：空指针

Null Pointers and Wild Pointers

Null pointer: a pointer variable pointing to the space with memory number 0

Purpose: initialize pointer variables

Note: the memory pointed to by a null pointer cannot be accessed

Example 1: null pointer

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int main() {

	//指针变量p指向内存地址编号为0的空间
	int * p = NULL;

	//访问空指针报错 
	//内存编号0 ~255为系统占用内存，不允许用户访问
	cout << *p << endl;

	system("pause");

	return 0;
}

野指针：指针变量指向非法的内存空间

示例2：野指针

Wild pointer: a pointer variable pointing to an illegal memory space

Example 2: wild pointer

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int main() {

	//指针变量p指向内存地址编号为0x1100的空间
	int * p = (int *)0x1100;

	//访问野指针报错 
	cout << *p << endl;

	system("pause");

	return 0;
}

总结：空指针和野指针都不是我们申请的空间，因此不要访问。

Summary: neither null pointers nor wild pointers point to space we allocated, so do not access them.

const修饰指针

const修饰指针有三种情况

  1. const修饰指针 — 常量指针
  2. const修饰常量 — 指针常量
  3. const即修饰指针，又修饰常量

示例：

const Modifying Pointers

There are three cases where const modifies pointers

  1. const modifies the pointer — constant pointer
  2. const modifies the constant — pointer constant
  3. const modifies both the pointer and the constant

Example:

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int main() {

	int a = 10;
	int b = 10;

	//const修饰的是指针，指针指向可以改，指针指向的值不可以更改
	const int * p1 = &a; 
	p1 = &b; //正确
	//*p1 = 100;  报错
	

	//const修饰的是常量，指针指向不可以改，指针指向的值可以更改
	int * const p2 = &a;
	//p2 = &b; //错误
	*p2 = 100; //正确

    //const既修饰指针又修饰常量
	const int * const p3 = &a;
	//p3 = &b; //错误
	//*p3 = 100; //错误

	system("pause");

	return 0;
}

技巧：看const右侧紧跟着的是指针还是常量, 是指针就是常量指针，是常量就是指针常量

Tip: check whether what immediately follows const on the right is a pointer or a constant. If it is a pointer, it is a constant pointer; if it is a constant, it is a pointer constant

指针和数组

**作用：**利用指针访问数组中元素

示例：

Pointers and Arrays

Purpose: use pointers to access the elements in an array

Example:

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int main() {

	int arr[] = { 1,2,3,4,5,6,7,8,9,10 };

	int * p = arr;  //指向数组的指针

	cout << "第一个元素： " << arr[0] << endl;
	cout << "指针访问第一个元素： " << *p << endl;

	for (int i = 0; i < 10; i++)
	{
		//利用指针遍历数组
		cout << *p << endl;
		p++;
	}

	system("pause");

	return 0;
}

指针和函数

**作用：**利用指针作函数参数，可以修改实参的值

示例：

Pointers and Functions

Purpose: use pointers as function parameters to modify the value of actual parameters

Example:

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//值传递
void swap1(int a ,int b)
{
	int temp = a;
	a = b; 
	b = temp;
}
//地址传递
void swap2(int * p1, int *p2)
{
	int temp = *p1;
	*p1 = *p2;
	*p2 = temp;
}

int main() {

	int a = 10;
	int b = 20;
	swap1(a, b); // 值传递不会改变实参

	swap2(&a, &b); //地址传递会改变实参

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

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

	system("pause");

	return 0;
}

总结：如果不想修改实参，就用值传递，如果想修改实参，就用地址传递

Summary: if you do not want to modify the actual parameters, use pass by value; if you want to modify them, use pass by address

指针、数组、函数

**案例描述：**封装一个函数，利用冒泡排序，实现对整型数组的升序排序

例如数组：int arr[10] = { 4,3,6,9,1,2,10,8,7,5 };

示例：

Pointers, Arrays, and Functions

Case description: encapsulate a function that uses bubble sort to sort an integer array in ascending order

For example, the array: int arr[10] = { 4,3,6,9,1,2,10,8,7,5 };

Example:

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//冒泡排序函数
void bubbleSort(int * arr, int len)  //int * arr 也可以写为int arr[]
{
	for (int i = 0; i < len - 1; i++)
	{
		for (int j = 0; j < len - 1 - i; j++)
		{
			if (arr[j] > arr[j + 1])
			{
				int temp = arr[j];
				arr[j] = arr[j + 1];
				arr[j + 1] = temp;
			}
		}
	}
}

//打印数组函数
void printArray(int arr[], int len)
{
	for (int i = 0; i < len; i++)
	{
		cout << arr[i] << endl;
	}
}

int main() {

	int arr[10] = { 4,3,6,9,1,2,10,8,7,5 };
	int len = sizeof(arr) / sizeof(int);

	bubbleSort(arr, len);

	printArray(arr, len);

	system("pause");

	return 0;
}

总结：当数组名传入到函数作为参数时，被退化为指向首元素的指针

Summary: when an array name is passed into a function as a parameter, it decays into a pointer to the first element

结构体

结构体基本概念

结构体属于用户自定义的数据类型，允许用户存储不同的数据类型

Structures

Basic Concepts of Structures

A structure is a user==-defined data type== that allows users to store different data types

结构体定义和使用

语法：struct 结构体名 { 结构体成员列表 }；

通过结构体创建变量的方式有三种：

  • struct 结构体名 变量名
  • struct 结构体名 变量名 = { 成员1值 ， 成员2值…}
  • 定义结构体时顺便创建变量

示例：

Defining and Using Structures

Syntax: struct structure name { list of structure members };

There are three ways to create variables through a structure:

  • struct structure name variable name
  • struct structure name variable name = { member 1 value, member 2 value…}
  • Create the variable while defining the structure

Example:

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//结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
}stu3; //结构体变量创建方式3 


int main() {

	//结构体变量创建方式1
	struct student stu1; //struct 关键字可以省略

	stu1.name = "张三";
	stu1.age = 18;
	stu1.score = 100;
	
	cout << "姓名：" << stu1.name << " 年龄：" << stu1.age  << " 分数：" << stu1.score << endl;

	//结构体变量创建方式2
	struct student stu2 = { "李四",19,60 };

	cout << "姓名：" << stu2.name << " 年龄：" << stu2.age  << " 分数：" << stu2.score << endl;


	stu3.name = "王五";
	stu3.age = 18;
	stu3.score = 80;
	

	cout << "姓名：" << stu3.name << " 年龄：" << stu3.age  << " 分数：" << stu3.score << endl;

	system("pause");

	return 0;
}

总结1：定义结构体时的关键字是struct，不可省略

总结2：创建结构体变量时，关键字struct可以省略

总结3：结构体变量利用操作符 ‘’.’’ 访问成员

Summary 1: the keyword when defining a structure is struct, which cannot be omitted

Summary 2: when creating a structure variable, the keyword struct can be omitted

Summary 3: structure variables use the operator ‘’.’’ to access members

结构体数组

**作用：**将自定义的结构体放入到数组中方便维护

语法：struct 结构体名 数组名[元素个数] = { {} , {} , ... {} }

示例：

Arrays of Structures

Purpose: put custom structures into an array for easier maintenance

Syntax: struct structure name array name[number of elements] = { {} , {} , ... {} }

Example:

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//结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
}

int main() {
	
	//结构体数组
	struct student arr[3]=
	{
		{"张三",18,80 },
		{"李四",19,60 },
		{"王五",20,70 }
	};

	for (int i = 0; i < 3; i++)
	{
		cout << "姓名：" << arr[i].name << " 年龄：" << arr[i].age << " 分数：" << arr[i].score << endl;
	}

	system("pause");

	return 0;
}

结构体指针

**作用：**通过指针访问结构体中的成员

  • 利用操作符 ->可以通过结构体指针访问结构体属性

示例：

Structure Pointers

Purpose: access the members in a structure through pointers

  • Use the operator -> to access structure attributes through a structure pointer

Example:

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//结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
};


int main() {
	
	struct student stu = { "张三",18,100, };
	
	struct student * p = &stu;
	
	p->score = 80; //指针通过 -> 操作符可以访问成员

	cout << "姓名：" << p->name << " 年龄：" << p->age << " 分数：" << p->score << endl;
	
	system("pause");

	return 0;
}

总结：结构体指针可以通过 -> 操作符 来访问结构体中的成员

Summary: a structure pointer can access the members of a structure through the -> operator

结构体嵌套结构体

作用： 结构体中的成员可以是另一个结构体

**例如：**每个老师辅导一个学员，一个老师的结构体中，记录一个学生的结构体

示例：

Nested Structures

Purpose: a member of a structure can be another structure

For example: each teacher tutors one student, and the structure of a teacher records the structure of a student

Example:

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//学生结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
};

//教师结构体定义
struct teacher
{
    //成员列表
	int id; //职工编号
	string name;  //教师姓名
	int age;   //教师年龄
	struct student stu; //子结构体 学生
};


int main() {

	struct teacher t1;
	t1.id = 10000;
	t1.name = "老王";
	t1.age = 40;

	t1.stu.name = "张三";
	t1.stu.age = 18;
	t1.stu.score = 100;

	cout << "教师 职工编号： " << t1.id << " 姓名： " << t1.name << " 年龄： " << t1.age << endl;
	
	cout << "辅导学员 姓名： " << t1.stu.name << " 年龄：" << t1.stu.age << " 考试分数： " << t1.stu.score << endl;

	system("pause");

	return 0;
}

**总结：**在结构体中可以定义另一个结构体作为成员，用来解决实际问题

Summary: another structure can be defined as a member inside a structure to solve practical problems

结构体做函数参数

**作用：**将结构体作为参数向函数中传递

传递方式有两种：

  • 值传递
  • 地址传递

示例：

Structures as Function Parameters

Purpose: pass a structure as a parameter to a function

There are two ways to pass it:

  • Pass by value
  • Pass by address

Example:

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//学生结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
};

//值传递
void printStudent(student stu )
{
	stu.age = 28;
	cout << "子函数中 姓名：" << stu.name << " 年龄： " << stu.age  << " 分数：" << stu.score << endl;
}

//地址传递
void printStudent2(student *stu)
{
	stu->age = 28;
	cout << "子函数中 姓名：" << stu->name << " 年龄： " << stu->age  << " 分数：" << stu->score << endl;
}

int main() {

	student stu = { "张三",18,100};
	//值传递
	printStudent(stu);
	cout << "主函数中 姓名：" << stu.name << " 年龄： " << stu.age << " 分数：" << stu.score << endl;

	cout << endl;

	//地址传递
	printStudent2(&stu);
	cout << "主函数中 姓名：" << stu.name << " 年龄： " << stu.age  << " 分数：" << stu.score << endl;

	system("pause");

	return 0;
}

总结：如果不想修改主函数中的数据，用值传递，反之用地址传递

Summary: if you do not want to modify the data in the main function, use pass by value; otherwise, use pass by address

结构体中 const使用场景

**作用：**用const来防止误操作

示例：

Using const in Structures

Purpose: use const to prevent accidental operations

Example:

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//学生结构体定义
struct student
{
	//成员列表
	string name;  //姓名
	int age;      //年龄
	int score;    //分数
};

//const使用场景
void printStudent(const student *stu) //加const防止函数体中的误操作
{
	//stu->age = 100; //操作失败，因为加了const修饰
	cout << "姓名：" << stu->name << " 年龄：" << stu->age << " 分数：" << stu->score << endl;

}

int main() {

	student stu = { "张三",18,100 };

	printStudent(&stu);

	system("pause");

	return 0;
}

结构体案例

Structure Case Studies

案例1

案例描述：

学校正在做毕设项目，每名老师带领5个学生，总共有3名老师，需求如下

设计学生和老师的结构体，其中在老师的结构体中，有老师姓名和一个存放5名学生的数组作为成员

学生的成员有姓名、考试分数，创建数组存放3名老师，通过函数给每个老师及所带的学生赋值

最终打印出老师数据以及老师所带的学生数据。

示例：

Case 1

Case description:

The school is working on a graduation project. Each teacher leads 5 students, and there are 3 teachers in total. The requirements are as follows:

Design structures for students and teachers. In the teacher structure, there is the teacher’s name and an array of 5 students as members

The student members include name and exam score. Create an array to store 3 teachers, and assign values to each teacher and their students through a function

Finally, print the teacher data and the data of the students led by each teacher.

Example:

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struct Student
{
	string name;
	int score;
};
struct Teacher
{
	string name;
	Student sArray[5];
};

void allocateSpace(Teacher tArray[] , int len)
{
	string tName = "教师";
	string sName = "学生";
	string nameSeed = "ABCDE";
	for (int i = 0; i < len; i++)
	{
		tArray[i].name = tName + nameSeed[i];
		
		for (int j = 0; j < 5; j++)
		{
			tArray[i].sArray[j].name = sName + nameSeed[j];
			tArray[i].sArray[j].score = rand() % 61 + 40;
		}
	}
}

void printTeachers(Teacher tArray[], int len)
{
	for (int i = 0; i < len; i++)
	{
		cout << tArray[i].name << endl;
		for (int j = 0; j < 5; j++)
		{
			cout << "\t姓名：" << tArray[i].sArray[j].name << " 分数：" << tArray[i].sArray[j].score << endl;
		}
	}
}

int main() {

	srand((unsigned int)time(NULL)); //随机数种子 头文件 #include <ctime>

	Teacher tArray[3]; //老师数组

	int len = sizeof(tArray) / sizeof(Teacher);

	allocateSpace(tArray, len); //创建数据

	printTeachers(tArray, len); //打印数据
	
	system("pause");

	return 0;
}

案例2

案例描述：

设计一个英雄的结构体，包括成员姓名，年龄，性别;创建结构体数组，数组中存放5名英雄。

通过冒泡排序的算法，将数组中的英雄按照年龄进行升序排序，最终打印排序后的结果。

五名英雄信息如下：

Case 2

Case description:

Design a structure for heroes, including the members name, age, and gender; create a structure array to store 5 heroes.

Use the bubble sort algorithm to sort the heroes in the array by age in ascending order, and finally print the sorted results.

The information of the five heroes is as follows:

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{"刘备",23,"男"},
{"关羽",22,"男"},
{"张飞",20,"男"},
{"赵云",21,"男"},
{"貂蝉",19,"女"},

示例：

Example:

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//英雄结构体
struct hero
{
	string name;
	int age;
	string sex;
};
//冒泡排序
void bubbleSort(hero arr[] , int len)
{
	for (int i = 0; i < len - 1; i++)
	{
		for (int j = 0; j < len - 1 - i; j++)
		{
			if (arr[j].age > arr[j + 1].age)
			{
				hero temp = arr[j];
				arr[j] = arr[j + 1];
				arr[j + 1] = temp;
			}
		}
	}
}
//打印数组
void printHeros(hero arr[], int len)
{
	for (int i = 0; i < len; i++)
	{
		cout << "姓名： " << arr[i].name << " 性别： " << arr[i].sex << " 年龄： " << arr[i].age << endl;
	}
}

int main() {

	struct hero arr[5] =
	{
		{"刘备",23,"男"},
		{"关羽",22,"男"},
		{"张飞",20,"男"},
		{"赵云",21,"男"},
		{"貂蝉",19,"女"},
	};

	int len = sizeof(arr) / sizeof(hero); //获取数组元素个数

	bubbleSort(arr, len); //排序

	printHeros(arr, len); //打印

	system("pause");

	return 0;
}