js实现单向链表

1. add() 添加元素
2. clear() 清空链表
3. contains(data) 是否包含元素
4. display() 显示链表
5. get(position) 得到索引位置的元素
6. isEmpty() 链表是否为空
7. remove(position) 移除索引位置的元素
8. reverse() 倒置链表
9. set(position, data) 向链表指定位置设置修改元素
10. size() 返回链表的长度

var Node = function (data) {
  this.data = data;
  this.next = null;
};

var LList = function () {
  this.firstNode = null;
  this.lastNode = null;
  this.length = 0;
};

LList.prototype = {
  clear: function () {
    this.firstNode = null;
    this.lastNode = null;
    this.length = 0;
  },

  get: function (position) {
    var currentNode = this.firstNode;
    for (var i = 1; i < position + 1; i++) {
      currentNode = currentNode.next;
    }
    return currentNode;
  },
  isEmpty: function () {
    var result = false;
    if (this.length == 0 && this.firstNode == null) {
      result = true;
    }
    return result;
  },
  add: function () {
    if (arguments.length == 1) {
      data = arguments[0];
      var newNode = new Node(data);
      if (this.isEmpty()) {
        this.firstNode = newNode;
      } else {
        this.lastNode.next = newNode;
      }
      this.lastNode = newNode;
      this.length++;
      return true;
    } else if (arguments.length == 2) {
      var isSuccessful = true;
      var position = arguments[0];
      var data = arguments[1];
      if (position < this.length + 1) {
        var newNode = new Node(data);
        if (this.isEmpty()) {
          this.firstNode = newNode;
          this.lastNode = newNode;
        } else if (position == this.length) {
          this.lastNode.next = newNode;
          this.lastNode = newNode;
        } else if (position == 0) {
          newNode.next = this.firstNode;
          this.firstNode = newNode;
        } else {
          var nodeBefore = this.get(position - 1);
          var nodeAfter = nodeBefore.next;
          newNode.next = nodeAfter;
          nodeBefore.next = newNode;
        }
        this.length++;
      } else {
        isSuccessful = false;
      }
      return isSuccessful;
    }
  },
  display: function () {
    var str = ‘‘;
    var currentNode = this.firstNode;
    while (currentNode != null) {
      str += currentNode.data + ‘, ‘
      currentNode = currentNode.next;
    }
    str = str.substr(0, str.length - 2);
    console.log(str);
  },
  remove: function (position) {
    var result = null;
    if (!this.isEmpty() && (position < this.length)) {
      if (position == 0) {
        result = this.firstNode.data;
        this.firstNode = this.firstNode.next;
        this.lastNode = null;
      } else {
        var nodeBefore = this.get(position - 1);
        var nodeToRemove = nodeBefore.next;
        var nodeAfter = nodeToRemove.next;
        nodeBefore.next = nodeAfter;
        result = nodeToRemove.data;
        if (position == this.length - 1) {
          this.lastNode = nodeBefore;
        }
      }
      this.length--;
    }
    return result;
  },
  set: function (position, data) {
    var isSuccessfule = true;
    if (!this.isEmpty() && (position < this.length)) {
      var desireNode = this.get(position);
      desireNode.data = data;
    } else {
      isSuccessfule = false;
    }
    return isSuccessfule;
  },
  contains: function (data) {
    var found = false;
    var currentNode = this.firstNode;

    while (!found && (currentNode != null)) {
      if (data === currentNode.data) {
        found = true;
      } else {
        currentNode = currentNode.next;
      }
    }
    return found;
  },
  size: function() {
    return this.length;
  },
  reverse: function() {
    var newList = new LList();
    for(var i=this.length-1; i>=0; i--) {
      newList.add(this.get(i).data);
    }
    return newList;
  }
};