/*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