/**
* Initialize your data structure here.
*/
var MyQueue = function () {
// 初始化两个栈 一个用来存放入队的元素 另一个存放出队的元素
this.inStack = [];
this.outStack = [];
};
/**
* Push element x to the back of queue.
* @param {number} x
* @return {void}
*/
MyQueue.prototype.push = function (x) {
// 入队
this.inStack.push(x);
};
/**
* Removes the element from in front of queue and returns that element.
* @return {number}
*/
MyQueue.prototype.pop = function () {
// 出队操作 如果出队的栈中没有元素 则从入队的栈中转移元素
if (!this.outStack.length) {
this.transfer();
}
// 弹出出栈的最新的元素 即出队操作
return this.outStack.pop();
};
/**
* Get the front element.
* @return {number}
*/
MyQueue.prototype.peek = function () {
// 返回队头元素
if (!this.outStack.length) {
this.transfer();
}
return this.outStack[this.outStack.length - 1];
};
/**
* Returns whether the queue is empty.
* @return {boolean}
*/
MyQueue.prototype.empty = function () {
// 判断队列是否为空 则校验出队和入队的栈中是否长度为 0
return this.outStack.length === 0 && this.inStack.length === 0;
};
// 执行从 inStack 转移元素到 outStack
MyQueue.prototype.transfer = function () {
while (this.inStack.length) {
this.outStack.push(this.inStack.pop());
}
};
/**
* 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()
*/