// 链表
class Link {
  constructor() {
    this.length = 0; //链表的长度
    this.head = null; //链表的指针
  }
  // 节点实例
  _node(data) {
    function node(data) {
      this.data = data
      this.next = null
    }
    return new node(data)
  }

  // 追加节点
  append(data) {
    const newNode = this._node(data)
    if (this.length === 0) {
      // 判断添加的是不是第一个节点,如果是第一个节点,就直接添加
      this.head = newNode;
    } else {
      // 不是第一个先找到最后一个然后在往后追加
      let curr = this.head;
      while (curr.next) {
        curr = curr.next
      }
      curr.next = newNode
    }
    this.length++;
  }
  // 在某一位置插入
  insert(position, data) {
    // 如果是插入第一个和最后一个,交给append处理
    const newNode = this._node(data)
    if (position > this.length) return false
    if (position == 0 || position == this.length) {
      this.append(data)
    } else {
      // 在中间插入,先找到前一个node 改变指向
      let index = 0; //遍历使用
      let curr = this.head //当前指针
      let previous = null;
      while (index++ < position) {
        // 循环找到要插入的节点位置
        previous = curr;
        curr = curr.next;
      }
      // 改变节点的指向
      previous.next = newNode;
      newNode.next = curr;
    }
    this.length++;
    return true
  }
  // 获得对应位置上的数据 传一个参数是获取,传两个参数是替换
  get(position, data) {
    if (this.length == 0 || position > this.length) return false
    let index = 0;
    let curr = this.head
    while (index++ != position) {
      curr = curr.next
    }
    if (data) {
      curr.data = data
      return true
    }
    return curr.data
  }
  // 获得对应数据的下标
  indexOf(data) {
    if (!data) return false;
    let index = 0;
    let curr = this.head;
    while (index++ < this.length) {
      if (curr.data == data) {
        return index - 1;
      }
      curr = curr.next;
    }
  }
  // 删除对应下标的元素
  remove(position) {
    if (this.length == 0 || position > this.length) return false
    let index = 0;
    let curr = this.head
    let previous = null;
    while (index++ != position) {
      previous = curr
      curr = curr.next
    }
    previous.next = curr.next
    this.length--;
    return true
  }
}
const link = new Link()
link.append('11')
link.append('12')
console.log(link.remove(1))
console.log(link)