【简单】232. 用栈实现队列

【题目】
来源：leetcode
链接：https://leetcode-cn.com/problems/implement-queue-using-stacks/
【代码】两个栈模拟一个队列
执行用时 :0 ms, 在所有 C++ 提交中击败了100.00% 的用户
内存消耗 :7 MB, 在所有 C++ 提交中击败了100.00%的用户

class MyQueue {
private:
    stack<int> s1,s2;
public:
    /** Initialize your data structure here. */
    MyQueue() {
    }
    /** Push element x to the back of queue. */
    void push(int x) {
        s1.push(x);
    }
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int x=peek();
        s2.pop();
        return x;
    }
    /** Get the front element. */
    int peek() {
        if(!s2.empty())
            return s2.top();
        while(!s1.empty()){
            s2.push(s1.top());
            s1.pop();
        }
        return s2.top();
    }
    /** Returns whether the queue is empty. */
    bool empty() {
        if(s1.empty()&&s2.empty())
            return true;
        return false;
    }
};
/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue* obj = new MyQueue();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->peek();
 * bool param_4 = obj->empty();
 */