用两个栈实现队列

• 无语，就是两个栈倒来倒去

class MyQueue {
public:
    stack<int> st;
    stack<int> tmp;
    /** Initialize your data structure here. */
    MyQueue() {
        
    }
    
    /** Push element x to the back of queue. */
    void push(int x) {
        st.push(x);
    }
    
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int res;
        while(st.size())
        {
            res=st.top();
            tmp.push(res);
            st.pop();
        }
        int t;
        tmp.pop();
        while(tmp.size())
        {
            t=tmp.top();
            st.push(t);
            tmp.pop();
        }
        return res;
    }
    
    /** Get the front element. */
    int peek() {
        int res;
        while(st.size())
        {
            res=st.top();
            tmp.push(res);
            st.pop();
        }
        int t;
        while(tmp.size())
        {
            t=tmp.top();
            st.push(t);
            tmp.pop();
        }
        return res;
    }
    
    /** Returns whether the queue is empty. */
    bool empty() {
        return !st.size();
    }
};

/**
 * 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();
 */