题目描述

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 )

提示：

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

测试用例

用例1：

• 输入：["CQueue","appendTail","deleteHead","deleteHead","deleteHead"] [[],[3],[],[],[]]
• 输出：[null,null,3,-1,-1]

用例2：

• 输入：["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"] [[],[],[5],[2],[],[]]
• 输出：[null,-1,null,null,5,2]

思路

instack栈放入数据[1, 2, 3] ，outstack 输出数据 输出时先看outStack有没有，有就outStack.pop()，没有就把inStack中的内容放到outStack，然后输出outStack.pop()

代码实现

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

// instack栈放入数据 [1, 2, 3]
// outstack 输出数据
// 输出时先看outStack有没有
// 有就outStack.pop
// 没有就把inStack中的内容放到outStack，然后输出outStack

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

/**
* @return {number}
*/
CQueue.prototype.deleteHead = function() {

  if(this.inStack.length == 0 && this.outStack.length == 0){
      return -1;
  }

  if(this.outStack.length > 0){
      return this.outStack.pop();
  }
  else{
      while(this.inStack.length > 0){
          this.outStack.push(this.inStack.pop());
      }
      return this.outStack.pop();
  }
  
};

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

var obj = new CQueue()
console.log("初始化: ", obj);
obj.appendTail(3);
console.log("obj_1: ", obj);
obj.appendTail(4);
obj.appendTail(54);
obj.appendTail(34);
obj.appendTail(24);
console.log("obj_2: ", obj);
var test = obj.deleteHead();
console.log("test: ", test);


var test = obj.deleteHead();
console.log("test: ", test);
var test = obj.deleteHead();
console.log("test: ", test);
var test = obj.deleteHead();
console.log("test: ", test);
var test = obj.deleteHead();
console.log("test: ", test);
var test = obj.deleteHead();
console.log("test: ", test);
console.log("obj_3: ", obj);