【leetcode】 232. 用栈实现队列

var MyQueue = function() {
    this.input = [];
    this.output = [];
};

MyQueue.prototype.move = function(x) {
    if(this.output.length) {
        return true;
    }
    this.output = this.input.reverse().concat(this.output);
    this.input = [];
}

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

/**
 * @return {number}
 */
MyQueue.prototype.pop = function() {
    this.move();
    return this.output.pop();
};

/**
 * @return {number}
 */
MyQueue.prototype.peek = function() {
    this.move();
    return this.output[this.output.length - 1];
};

/**
 * @return {boolean}
 */
MyQueue.prototype.empty = function() {
    return !this.output.length && !this.input.length
};

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