2023-9-4

9-4

队列

题号232. 用栈实现队列

题目请你仅使用两个栈实现先入先出队列。队列应当支持一般队列支持的所有操作（push、pop、peek、empty）：

思路 使用两个栈实现，一个入栈，一个出栈

var MyQueue = function() {
    this.is = []
    this.os = []
};

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

/**
 * @return {number}
 */
MyQueue.prototype.pop = function() {
    if(!this.os.length){
        while(this.is.length){
            this.os.push(this.is.pop())
        }
    }
    return this.os.pop()
};

/**
 * @return {number}
 */
MyQueue.prototype.peek = function() {
    if(!this.os.length){
        while(this.is.length){
            this.os.push(this.is.pop())
        }
    }
    return this.os[this.os.length-1]
};

/**
 * @return {boolean}
 */
MyQueue.prototype.empty = function() {
    return !this.os.length&&!this.is.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()
 */