关于javascript:javascript-数据结构系列-二-双向链表

明天持续讲数据结构双向链表 DoublyLinkedList具体实现
波及两个类 DoublyLinkedListNode DoublyLinkedList
首先, 看一下 DoublyLinkedListNode 类实现，代码如下

export default class DoublyLinkedListNode {constructor(value, next = null, previous = null) {
    this.value = value;
    this.next = next;
    this.previous = previous;
  }

  toString(callback) {return callback ? callback(this.value) : `${this.value}`;
  }
}

其次，DoublyLinkedList 实现，构造函数如下

export default class DoublyLinkedList {
  /**
   * @param {Function} [comparatorFunction]
   */
  constructor(comparatorFunction) {
    /** @var DoublyLinkedListNode */
    this.head = null;

    /** @var DoublyLinkedListNode */
    this.tail = null;

    this.compare = new Comparator(comparatorFunction);
  }
}

append 办法

  /**
   * @param {*} value
   * @return {DoublyLinkedList}
   */
  append(value) {const newNode = new DoublyLinkedListNode(value);

    // If there is no head yet let's make new node a head.
    if (!this.head) {
      this.head = newNode;
      this.tail = newNode;

      return this;
    }

    // Attach new node to the end of linked list.
    this.tail.next = newNode;

    // Attach current tail to the new node's previous reference.
    newNode.previous = this.tail;

    // Set new node to be the tail of linked list.
    this.tail = newNode;

    return this;
  }

delete 办法

  /**
   * @param {*} value
   * @return {DoublyLinkedListNode}
   */
  delete(value) {if (!this.head) {return null;}

    let deletedNode = null;
    let currentNode = this.head;

    while (currentNode) {if (this.compare.equal(currentNode.value, value)) {
        deletedNode = currentNode;

        if (deletedNode === this.head) {
          // If HEAD is going to be deleted...

          // Set head to second node, which will become new head.
          this.head = deletedNode.next;

          // Set new head's previous to null.
          if (this.head) {this.head.previous = null;}

          // If all the nodes in list has same value that is passed as argument
          // then all nodes will get deleted, therefore tail needs to be updated.
          if (deletedNode === this.tail) {this.tail = null;}
        } else if (deletedNode === this.tail) {
          // If TAIL is going to be deleted...

          // Set tail to second last node, which will become new tail.
          this.tail = deletedNode.previous;
          this.tail.next = null;
        } else {
          // If MIDDLE node is going to be deleted...
          const previousNode = deletedNode.previous;
          const nextNode = deletedNode.next;

          previousNode.next = nextNode;
          nextNode.previous = previousNode;
        }
      }

      currentNode = currentNode.next;
    }

    return deletedNode;
  }

find 办法

  /**
   * @param {Object} findParams
   * @param {*} findParams.value
   * @param {function} [findParams.callback]
   * @return {DoublyLinkedListNode}
   */
  find({value = undefined, callback = undefined}) {if (!this.head) {return null;}

    let currentNode = this.head;

    while (currentNode) {
      // If callback is specified then try to find node by callback.
      if (callback && callback(currentNode.value)) {return currentNode;}

      // If value is specified then try to compare by value..
      if (value !== undefined && this.compare.equal(currentNode.value, value)) {return currentNode;}

      currentNode = currentNode.next;
    }

    return null;
  }

reverse 办法

  /**
   * Reverse a linked list.
   * @returns {DoublyLinkedList}
   */
  reverse() {
    let currNode = this.head;
    let prevNode = null;
    let nextNode = null;

    while (currNode) {
      // Store next node.
      nextNode = currNode.next;
      prevNode = currNode.previous;

      // Change next node of the current node so it would link to previous node.
      currNode.next = prevNode;
      currNode.previous = nextNode;

      // Move prevNode and currNode nodes one step forward.
      prevNode = currNode;
      currNode = nextNode;
    }

    // Reset head and tail.
    this.tail = this.head;
    this.head = prevNode;

    return this;
  }