leetcode-232.cpp

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

    }

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

        while(!st2.empty())
        {
            st1.push(st2.top());
            st2.pop();
        }
        st1.push(x);

        while(!st1.empty())
        {
            st2.push(st1.top());
            st1.pop();
        }
    }

    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        int num=st2.top();
        st2.pop();
        return num;
    }

    /** Get the front element. */
    int peek() {
        return st2.top();
    }

    /** Returns whether the queue is empty. */
    bool empty() {
        return st2.empty();
    }
    private:
    stack<int> st1;
    stack<int> st2;
};

/**
 * 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();
 */