leetcode255、两个队列实现栈

#include <queue>
#include <iostream>

using namespace std;

class MyStack
{
public:
    // Initialize your data structure here.
    MyStack(){}

    // Push element x onto stack.
    void push(int x)
    {
        queue<int> temp_queue;  // 空队列
        temp_queue.push(x);
        // 将_data中所有数据依次添加到temp_queue中
        while (!_data.empty())
        {
            temp_queue.push(_data.front());
            _data.pop();
        }
        // 将temp_queue中所有数据依次添加到_data中
        while (!temp_queue.empty())
        {
            _data.push(temp_queue.front());
            temp_queue.pop();
        }
    }

    // Removes the element on top of the stack and returns that element.
    int pop()
    {
        int x = _data.front();
        _data.pop();
        return x;
    }

    // Get the top element.
    int top()
    {
        int x = _data.front();
        return x;
    }

    // Returns whether the stack is empty.
    bool empty()
    {
        return _data.empty();
    }
private:
    queue<int> _data;
};


int main()
{
    MyStack S;
    S.push(1);
    S.push(2);
    S.push(3);
    S.push(4);

    S.pop();

    S.push(5);
    return 0;
}