简单的LinkList实现

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class Node {
  constructor(data = -1, prev = null, next = null) {
    this.data = data
    this.prev = prev // 向前指针
    this.next = next // 向后指针
  }
}

class LinkList {
  constructor() {
    this.head = this.tail = null // 首、尾指针
    this.size = 0 // 元素个数
  }

  addHead(elem) {
    let elemNode = new Node(elem)
    if (this.size == 0) {
      this.head = this.tail = elemNode
      this.size++
    } else {
      this.head.prev = elemNode
      elemNode.next = this.head
      this.head = elemNode
      this.size++
    }
    return true
  }

  deleteHead() {
    if (this.size != 0) {
      let elem = this.head.data
      this.head.prev = null
      this.head = this.head.next
      this.size--
      return elem
    } else {
      console.log("list is empty")
      return
    }
  }

  addTail(elem) {
    let elemNode = new Node(elem)
    if (this.size == 0) {
      this.head = this.tail = elemNode
      this.size++
    } else {
      elemNode.prev = this.tail
      this.tail.next = elemNode
      this.tail = elemNode
      this.size++
    }
    return true
  }

  deleteTail() {
    if (this.size != 0) {
      let elem = this.tail.data
      this.tail.next = null
      this.tail = this.tail.prev
      this.size--
      return elem
    } else {
      console.log("list is empty")
      return
    }
  }

  display() {
    let current = this.head,
      count = this.size,
      str = ""
    while (count > 0) {
      str += current.data + " "
      current = current.next
      count--
    }
    console.log(str)
  }
}
let linklist = new LinkList()
linklist.addHead(1)
linklist.addHead(2)
linklist.addHead(3)
linklist.deleteHead()
linklist.addTail(4)
linklist.display()

结果

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