题目描述

请用栈实现一个队列，支持如下四种操作

样例

class MyQueue {
public:
    stack<int> myStack;
    stack<int> p;
    /** Initialize your data structure here. */
    MyQueue() {
    }

    /** Push element x to the back of queue. */
    void push(int x) {
        myStack.push(x);
    }

    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int len=myStack.size();
        for(int i=0;i<len-1;i++){
            p.push(myStack.top());
            myStack.pop();
        }
        int target=myStack.top();
        myStack.pop();
        while(!p.empty()){
            myStack.push(p.top());
            p.pop();
        }
        return target;
    }

    /** Get the front element. */
    int peek() {
        int len=myStack.size();
        for(int i=0;i<len-1;i++){
            p.push(myStack.top());
            myStack.pop();
        }
        int target=myStack.top();
        for(int i=0;i<len-1;i++){
            myStack.push(p.top());
            p.pop();
        }
        return target;

    }

    /** Returns whether the queue is empty. */
    bool empty() {
        return myStack.empty();
    }
};

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * bool param_4 = obj.empty();
 */