leetcode 用栈实现队列 简单

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

    /** Push element x to the back of queue. */
    void push(int x) {
        stk1.push(x);
    }

    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int ret = peek();
        stk2.pop();
        return ret;
    }

    /** Get the front element. */
    int peek() {
        if(stk2.empty()) {
            while(!stk1.empty()) {
                stk2.push(stk1.top());
                stk1.pop();
            }
        }
        return stk2.top();
    }

    /** Returns whether the queue is empty. */
    bool empty() {
        return stk1.empty() && stk2.empty();
    }

private:
    stack<int> stk1, stk2;
};