Queue.ts

// 声明队列内部对象类型
interface QueueObj {
  [propName: number]: any;
}

/**
 * 实现队列
 *    队列的基础方法: 入队、出队、返回队首元素、获取队列大小、判断队列是否为空、清空队列、获取队列内所有数据
 */
export default class Queue {
  private count: number;
  private lowestCount: number;
  private items: QueueObj;

  // 构造器
  constructor() {
    // 队列中的三个必要变量: 队列大小、队首元素、队列对象
    this.count = 0;
    this.lowestCount = 0;
    this.items = {};
  }

  // 入队
  enqueue(item: any) {
    // 队列的末尾添加元素: 将队列的大小作为key
    this.items[this.count] = item;
    this.count++;
  }

  // 出队
  dequeue() {
    if (this.isEmpty()) {
      return undefined;
    }
    const result = this.items[this.lowestCount];
    // 删除队首元素
    delete this.items[this.lowestCount];
    // 队首元素自增
    this.lowestCount++;
    return result;
  }

  // 返回队首元素
  peek() {
    if (this.isEmpty()) {
      return undefined;
    }
    return this.items[this.lowestCount];
  }

  // 队列大小: 队列的大小 - 队首元素
  size() {
    return this.count - this.lowestCount;
  }

  // 判断队列是否为空
  isEmpty() {
    return this.count - this.lowestCount === 0;
  }

  // 清空队列
  clear() {
    this.count = 0;
    this.lowestCount = 0;
    this.items = {};
  }

  // 获取队列内所有数据
  toString() {
    if (this.isEmpty()) {
      return "";
    }
    let objString = `${this.items[this.lowestCount]}`;
    for (let i = this.lowestCount + 1; i < this.count; i++) {
      objString = `${objString},${this.items[i]}`;
    }
    return objString;
  }
}