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queue

队列

1.创建类表示队列​

class Queue {
  constructor () {
    this.count = 0
    this.lowestCount = 0 // 第一个元素
    this.items = {}
  }
}

2.向队列添加元素​

新的项只能添加到队列末尾

enqueue (elements) {
  this.items[this.count] = elements
  this.count++
}

3.从队列移除元素​

遵循先进先出的原则，最先添加的项也最先被移除

dequeue () {
  if (this.isEmpty()) {
    return undefined
  }
  let result = this.items[this.lowestCount]
  delete this.items[this.lowestCount]
  this.lowestCount++
  return result
}

4.查看队列头元素​

peek () {
  if (this.isEmpty()) {
    return
  }
  return this.items[this.lowestCount]
}

5.检查队列是否为空​

isEmpty () {
  return this.size() === 0
}

6.获取队列长度​

size () {
  return this.count - this.lowestCount
}

7.清空队列​

clear () {
  this.items = {}
  this.lowestCount = 0
  this.count = 0
}

8.创建toString方法​

toString () {
  if (this.isEmpty()) {
    return
  }
  let str = ''
  for (let i = this.lowestCount; i < this.size(); i++) {
    str += `${this.items[i]}`
  }
  return str
}