javascript 数据结构系列 (二) 双向链表

博客说明

由于最近开始练习写作，文章所涉及的资料来自互联网整理和个人总结，意在于个人学习和经验汇总，如有什么地方侵权，请联系本人删除！

今天继续讲数据结构 双向链表 DoublyLinkedList具体实现
涉及两个类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 {
  constructor(comparatorFunction) {
    this.head = null;
    this.tail = null;

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

append 方法

  append(value) {
    const newNode = new DoublyLinkedListNode(value);
    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 方法

  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 方法

  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 方法

  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;
  }

以上代码实现了一个基本链表应具备方法，希望对学习数据结构同学有帮助，下一期将推出数据结构 栈，敬请关注!