js数据结构之链表（单链表、双向链表、循环链表）

首先，链表有以下特点：

1. 存储空间不固定，可灵活扩充

2.方便多次的插入和删除，效率较高

单链表

单链表是最常用的链表，其对数据的操作均为单项的，向后查找的。

/*
链表（基于对象）  此处为单链表
*/
function Node (ele) {
    this.element = ele;
    this.next = null;
}

function LinkedList () {
    this.head = new Node("head");  // 头结点
    this.find = find;   // 根据element值查找节点
    this.findPrevious = findPrevious;
    this.insert = insert;
    this.remove = remove;
    this.display = display;
}

function find (item) {
    var currNode = this.head;
    while(currNode.element !== item) {
        if(currNode.next === null) {
            return false;
        }
        currNode = currNode.next;
    }
    return currNode;
}

function findPrevious (item) {
    var currNode = this.head;
    while(currNode.next!==null&& currNode.next.element!=item){
        currNode = currNode.next;
    }
    return currNode;
}

function insert (newEleContent, item) {
    var newNode = new Node(newEleContent);
    var currNode = this.find(item);
    newNode.next = currNode.next;
    currNode.next = newNode;
}

function display () {
    var currNode = this.head;
    while(currNode.next !== null){
        console.log(currNode.next.element)
        currNode = currNode.next;
    }
}

function remove (item) {
    var currNode = this.find(item);
    var previousNode = this.findPrevious(currNode.element);
    previousNode.next = currNode.next;
    currNode = null;
}

双向链表

双向链表可以方便地对数据进行向前和向后查找（操作），如播放器正向播放音乐时用户存在上一曲和下一曲的操作需要，此时就用到了双向链表。

function Node (ele) {
    this.element = ele;
    this.next = null;
    this.previous = null;
}

function DuplexLinkedList () {
    this.head = new Node("head");
    this.find = find;
    this.findLast = findLast;
    this.remove = remove;
    this.insert = insert;
    this.display = display;
    this.displayReverse = displayReverse;
}

function find (item) {
    var currNode = this.head;
    while (currNode.element!==item) {
        currNode = currNode.next;
    }

    return currNode;
}

function remove (item) {
    var currNode = this.find(item);
    currNode.previous.next = currNode.next;
    if(currNode.next){
        currNode.next.previous = currNode.previous;
    }
    currNode = null;
}

function insert (eleContent, item) {
    var newNode = new Node(eleContent);
    var currNode = this.find(item);
    // 先操作新节点，否则会进死循环
    newNode.previous = currNode;
    newNode.next = currNode.next;
    currNode.next = newNode;
    if(currNode.next.previoue){
        currNode.next.previous = newNode;
    }
    console.log(newNode);

}

function findLast () {
    var currNode = this.head;
    while(currNode.next!==null){
        currNode = currNode.next;
    }
    return currNode;
}

function display () {
    var currNode = this.head;
    while (currNode.next!==null){
        console.log(currNode.next.element);
        currNode = currNode.next;
    }
}

function displayReverse () {
    var currNode = this.findLast();
    console.log(currNode);
    while(currNode.previous!==null){
        console.log(currNode.element);
        currNode = currNode.previous;
    }
}

循环链表

同理，循环链表是单向的，但是可以循环地查找。例如解决约瑟夫环问题

function Node (ele) {
    this.element = ele;
    this.next = null;
}

//循环链表需要将this.head.next指向this.head

function CirLinkedList () {
    this.head = new Node("head");
    this.head.next = this.head;
    this.find = find;
    this.findPrevious = findPrevious;
    this.insert = insert;
    this.remove = remove;
    this.display = display;
}

function find (item) {
    var currNode = this.head;
    while(currNode.element !== item) {
        if(currNode.next === null) {
            return false;
        }
        currNode = currNode.next;
    }
    return currNode;
}

function findPrevious (item) {
    var currNode = this.head;
    while(currNode.next!==null&& currNode.next.element!==item){
        currNode = currNode.next;
    }
    return currNode;
}

function insert (newEleContent, item) {
    var newNode = new Node(newEleContent);
    var currNode = this.find(item);
    newNode.next = currNode.next;
    currNode.next = newNode;
    console.log(newNode);
}

function display () {
    var currNode = this.head;
    // 循环输出判断需要增加next是不是头节点
    while(currNode.next.element != "head" && currNode.next.element!=="head" ){
        console.log(currNode.next.element);
        currNode = currNode.next;
    }
}

function remove (item) {
    var currNode = this.find(item);
    var previousNode = this.findPrevious(currNode.element);
    previousNode.next = currNode.next;
    currNode = null;
}