Leecode225 用队列实现栈

class MyStack {
public:
    /** Initialize your data structure here. */
    MyStack() {
    }
    /** Push element x onto stack. */
    void push(int x) {
        //添加一个临时队列
        std::queue<int> temp_queue;
        temp_queue.push(x);
        //只要队列数据不为空，就一直压入临时队列
        while(!_data.empty()){
            temp_queue.push(_data.front());
            _data.pop();
        }
        //只要临时队列不为空，就一直压入主队列
        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() {
        //直接返回队列的头部元素
        int x = _data.front();
        //弹出队列
        _data.pop();
        return x;
    }
    /** Get the top element. */
    int top() {
        //返回队列的头部元素
        return _data.front();
    }
    /** Returns whether the stack is empty. */
    bool empty() {
        //可以直接所使用的队列的empty()方法
        return _data.empty();
    }
private:
    std::queue<int> _data;
};
/**
 * Your MyStack object will be instantiated and called as such:
 * MyStack* obj = new MyStack();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->top();
 * bool param_4 = obj->empty();
 */