implement-stacok-using-queues.js

// 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).


var MyStack = function () {
    this.queue1 = [];
    this.queue2 = [];
};

MyStack.prototype.push = function (x) {
    this.queue2.push(x);

    while (this.queue1.length > 0) {
        this.queue2.push(this.queue1.shift());
    }

    [this.queue1, this.queue2] = [this.queue2, this.queue1];
};

MyStack.prototype.pop = function () {
    return this.queue1.shift();
};

MyStack.prototype.top = function () {
    return this.queue1[0];
};

MyStack.prototype.empty = function () {
    return this.queue1.length === 0;
};

/** 
 * 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()
 */