225.implement-stack-using-queues.cpp

/*
 * @lc app=leetcode id=225 lang=cpp
 *
 * [225] Implement Stack using Queues
 */

// @lc code=start
class MyStack {
public:
    /** Initialize your data structure here. */
    queue<int> *q1 = new queue<int>, *q2 = new queue<int>;
    MyStack() {
        
    }
    
    /** Push element x onto stack. */
    void push(int x) {
        q2->push(x);
        while (!q1->empty())
        {
            q2->push(q1->front());
            q1->pop();
        }
        swap(q1,q2);
    }
    
    /** Removes the element on top of the stack and returns that element. */
    int pop() {
        int t = q1->front();
        q1->pop();
        return t;
    }
    
    /** Get the top element. */
    int top() {
        return q1->front();
    }
    
    /** Returns whether the stack is empty. */
    bool empty() {
        return q1->empty();
    }
};

/**
 * Your MyStack object will be instantiated and called as such:
 * MyStack* obj = new MyStack();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->top();
 * bool param_4 = obj->empty();
 */
// @lc code=end