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#include <iostream>
using namespace std;

class A{
public:
    virtual void print(){
        cout << "A" << endl;
    }
};

class B:public A{
public:
    void print(){
        cout << "B" << endl;
    }
};

int main(){
    A b = B();
    b.print(); // 这样可以吗？
	return 0;
}

面试官问我这样可以吗？

我犹豫了好久好久… 也不知道可以不可以。

面试官看我答不出来，然后问我知道静态绑定和动态绑定吗？（这是在提示我了）

可我还是不知道可以还是不可以。😥

The interviewer asked me: can this be done?

I hesitated for a long, long time… and still didn’t know whether it could or couldn’t.

Seeing that I couldn’t answer, the interviewer then asked whether I knew about static binding and dynamic binding. (That was a hint to me.)

But I still didn’t know whether it could or couldn’t. 😥

写一些刷题常用数据结构

Some common data structures used in problem solving

提到 STL 算法，大家都知道很牛B。

但是想一想，除了 sort() , 你还会用啥呢？😂

最近抽时间把 STL 所有算法测试一遍，做到心里有个印象。

本文的这些示例基本上都来自于 cppreference.com 和 cplusplus.com

其实就是挨个看一遍，然后复制粘贴一下。

STL algorithms — everyone knows they are awesome.

But think about it: apart from sort(), what else do you actually use? 😂

I recently took some time to test all STL algorithms one by one, so I have a rough idea of what each one does.

The examples in this article basically come from cppreference.com and cplusplus.com

In fact, I just went through them one by one and copy-pasted.

起因

4 月 13 号早上八点多，我还在睡梦中，被 Telegram 的一条推送吵醒了。

很奇怪，我一个根本没人访问的 WebServer 小项目竟然会自己就宕机了😕。

上午十点睡醒了，起来看一眼日志吧。

好家伙，有人拿我 抄来 的小项目在练手？

Why It Happened

Around 8 am on April 13th, I was still fast asleep when I was woken up by a push notification on Telegram.

Strange — my little WebServer project, which nobody even visits, had crashed all by itself 😕.

I woke up again around 10 am and took a look at the logs.

Well well, someone is practicing on my copied little project?

再分享一道笔试题

Another Written Exam Question

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#include <iostream>
using namespace std;

int main(){
    
    int a[] = {1,2,3,4,5};
    int* p = (int*)(&a + 1);
    
    cout << *(a+1) << ',' << *(p-1) << endl;
    
    return 0;
}

问此程序的输出是多少？

错误答案是 2,1

What is the output of this program?

The wrong answer is 2,1

这是一道百度的笔试题

问：关于下面的程序输出为：

• A：1
• B：2
• C：3
• D：编译无法通过

A Baidu Written Test Question

Q: What does the following program output?

• A: 1
• B: 2
• C: 3
• D: It won’t compile

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#include <iostream>
using namespace std;

void test(int a,int b,int c){
    int *p = &b;
    cout << *(p-1) << endl;
}

int main(){
    test(1,2,3);
    return 0;
}

正确答案是…

The correct answer is…

C++ 中的 new

C++ 中使用 new 关键字来创建一个对象，创建对象的过程会产生以下操作：

1. 在内存中申请一块空间，大小为目标对象的大小，并获得该内存空间的地址。
2. 将该内存空间的地址转换为对象指针。
3. 通过对象指针调用该对象的构造函数。

new in C++

In C++, the new keyword is used to create an object, and the object creation process involves the following operations:

1. Allocate a block of memory, sized to the target object, and obtain the address of that memory.
2. Convert the address of that memory into an object pointer.
3. Invoke the object’s constructor through the object pointer.