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232. 用栈实现队列

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）：

实现 MyQueue 类：

void push(int x) 将元素 x 推到队列的末尾
int pop() 从队列的开头移除并返回元素
int peek() 返回队列开头的元素
boolean empty() 如果队列为空，返回 true ；否则，返回 false

示例

输入：
["MyQueue", "push", "push", "peek", "pop", "empty"]
[[], [1], [2], [], [], []]
输出：
[null, null, null, 1, 1, false]

解释：
MyQueue myQueue = new MyQueue();
myQueue.push(1); // queue is: [1]
myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue)
myQueue.peek(); // return 1
myQueue.pop(); // return 1, queue is [2]
myQueue.empty(); // return false

答案

var MyQueue = function() {
    this.inStack = [];
    this.outStack = [];
};

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

/**
 * @return {number}
 */
MyQueue.prototype.pop = function() {
    // 倒栈
    if(!this.outStack.length){
      while(this.inStack.length){
        this.outStack.push(this.inStack.pop())
      }
    }

    return this.outStack.pop();
};

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

/**
 * @return {boolean}
 */
MyQueue.prototype.empty = function() {
    return this.outStack.length === 0 && this.inStack.length === 0;
};

const myQueue = new MyQueue();
myQueue.push(1); // queue is: [1]
myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue)
myQueue.peek(); // return 1
myQueue.pop(); // return 1, queue is [2]
myQueue.empty(); // return false

console.log('myQueue',myQueue)

答案