/*双向链表
* */
function Node(element) {
  this.element = element;
  this.next = null;
  this.previous = null;//双向链表在这里需要增加一个previous属性
}
function LList() {
  this.head = new Node("head");
  this.find = find;
  this.insert = insert;
  this.display = display;
  this.remove = remove;
  this.findLast = findLast;
  this.dispReverse = dispReverse;//将链表反转
}
function dispReverse() {
  var currNode = this.head;
  currNode = this.findLast();
  var nodestr = "";
  while (!(currNode.previous == null)) {
    nodestr += " "+currNode.element;
    currNode = currNode.previous;
  }
  console.log("将链表反转后： "+nodestr);
}
function findLast() {
  var currNode = this.head;
  while (!(currNode.next == null)) {
    currNode = currNode.next;
  }
  return currNode;
}
function remove(item) {
  var currNode = this.find(item);
  if (!(currNode.next == null)) {
    currNode.previous.next = currNode.next;
    currNode.next.previous = currNode.previous;
    currNode.next = null;
    currNode.previous = null;
  }
}
// findPrevious is no longer needed
/*function findPrevious(item) {
 var currNode = this.head;
 while (!(currNode.next == null) &&
 (currNode.next.element != item)) {
 currNode = currNode.next;
 }
 return currNode;
 }*/
function display() {
  var currNode = this.head;
  var nodestr = "";
  while (!(currNode.next == null)) {
    nodestr += " "+currNode.next.element;
    currNode = currNode.next;
  }
  console.log(nodestr);
}
function find(item) {
  var currNode = this.head;
  while (currNode.element != item) {
    currNode = currNode.next;
  }
  return currNode;
}
function insert(newElement, item) {
  var newNode = new Node(newElement);
  var current = this.find(item);
  newNode.next = current.next;
  newNode.previous = current;//双向链表在这里需要设置新节点previous属性
  current.next = newNode;
}
var cities = new LList();
cities.insert("Conway", "head");
cities.insert("Russellville", "Conway");
cities.insert("Carlisle", "Russellville");
cities.insert("Alma", "Carlisle");
cities.display();//Conway Russellville Carlisle Alma
cities.remove("Carlisle");
cities.display();//Conway Russellville Alma
cities.dispReverse();// Alma Russellville Conway