implementStackusingQueues.js

////////////////////////////////////////////////Implement Stack using Queues/////////////////////////////////////////////
// Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack (push, top, pop, and empty).
// Implement the MyStack class:
// void push(int x) Pushes element x to the top of the stack.
// int pop() Removes the element on the top of the stack and returns it.
// int top() Returns the element on the top of the stack.
// boolean empty() Returns true if the stack is empty, false otherwise.
// Notes:
// You must use only standard operations of a queue, which means that only push to back, peek/pop from front, size and is empty operations are valid.
// Depending on your language, the queue may not be supported natively. You may simulate a queue using a list or deque
// (double-ended queue) as long as you use only a queue's standard operations.
// Example 1:
// Input
// ["MyStack", "push", "push", "top", "pop", "empty"]
// [[], [1], [2], [], [], []]
// Output
// [null, null, null, 2, 2, false]
//
// Explanation
// MyStack myStack = new MyStack();
// myStack.push(1);
// myStack.push(2);
// myStack.top(); // return 2
// myStack.pop(); // return 2
// myStack.empty(); // return False
const MyStack = function() {
    this.queue = [];
    this.queue2 = []
};

/**
 * @param {number} x
 * @return {void}
 */
MyStack.prototype.push = function(x) {
    this.queue.push(x)
};

/**
 * @return {number}
 */
MyStack.prototype.pop = function() {
    while (this.queue.length > 1) {
        this.queue2.push(this.queue.shift())
    }
    let poped = this.queue.shift()
    this.queue = this.queue2;
    this.queue2 = []
    return poped
};

/**
 * @return {number}
 */
MyStack.prototype.top = function() {
    return this.queue[this.queue.length-1]
};

/**
 * @return {boolean}
 */
MyStack.prototype.empty = function() {
    return this.queue.length ? false : true
};

/**
 * Your MyStack object will be instantiated and called as such:
 * var obj = new MyStack()
 * obj.push(x)
 * var param_2 = obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.empty()
 */