用两个栈实现队列

2020-03-25

用两个栈实现队列

用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ， 分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1)

说明:

• 1 <= values <= 10000
• 你最多会对 appendTail、deleteHead 进行 10000 次调用

示例:

输入:

["CQueue","appendTail","deleteHead","deleteHead"]

[[],[3],[],[]]

输出: [null,null,3,-1]

输入:

["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]

[[],[],[5],[2],[],[]]

输出: [null,-1,null,null,5,2]

题解:

思路1: 基础栈

左手倒右手。。。

 

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

/** 
 * @param {number} value
 * @return {void}
 */
CQueue.prototype.appendTail = function (value) {
  this.inStack.push(value);
};

/**
 * @return {number}
 */
CQueue.prototype.deleteHead = function () {
  let { inStack, outStack } = this;
  if (outStack.length === 0) {
    if (inStack.length > 0) {
      while (inStack.length > 0) {
        outStack.push(inStack.pop());
      }
    } else {
      return -1;
    }
  }
  return outStack.pop();
};

/**
 * Your CQueue object will be instantiated and called as such:
 * var obj = new CQueue()
 * obj.appendTail(value)
 * var param_2 = obj.deleteHead()
 */