数据结构JavaScript——单链表、循环链表

数据结构系列前言：

        数据结构作为程序员的基本知识，需要我们每个人牢牢掌握。近期我也展开了对数据结构的二次学习，来弥补当年挖的坑。。。。。。   当时上课的时候也就是跟着听课，没有亲自实现任何一种数据结构，更别提利用数据结构来解决问题了。  现在就来填坑了   在这里提醒看到我博客的孩子们，如果你还是在校生，永远不要轻视任何一门基础课的学习，这个时候挖的坑，要么需要用双倍的努力去填，要么会直接影响一个人的能力等等。。。。。。 千万别给自己挖坑

进入正题，关于链表的数据结构知识，这里简单介绍下：

        链表是一种物理存储单元上非线性、非连续性的数据结构（它在数据逻辑上是线性的），它的每个节点由两个域组成：数据域和指针域。数据域中存储实际数据，指针域则存储着指针信息，指向链表中的下一个元素或者上一个元素。正是由于指针的存在，链表的存储在物理单元是非连续性的。 

        链表的优点和缺点同样明显。和线性表相比，链表在添加和删除节点上的效率更高，因为其只需要修改指针信息即可完成操作，而不像线性表（数组）那样需要移动元素。同样的，链表的长度在理论上也是无限的（在存储器容量范围内），并可以动态变化长度，相比线性表优势很大。 相应的，由于线性表无法随机访问节点，只能通过指针顺着链表进行遍历查询来访问，故其访问数据元素的效率比较低。  

下面是JS部分

        这里面封装了的常用方法及描述：

方法描述append(element)  向链表尾部添加结点elementinsert(position,element) 向位置position处插入结点elementremoveAt(position) 按照索引值position删除结点remove(element) 搜索并删除给定结点elementremove() 删除链表中最后一个结点indexOf(element)查找并返回给定结点element的索引值isEmpty() 判断链表是否为空size() 获取链表长度toString() 转换为字符串输出getHead()获取头结点getTail() 获取尾结点

       对于各常用方法的算法描述在这里就不写了，相信大家都可以轻易读懂并理解，毕竟都是非常基础的知识了。

单链表：

function LinkedList(){/*节点定义*/var Node = function(element){this.element = element; //存放节点内容this.next = null; //指针}var length = 0, //存放链表长度    head = null; //头指针this.append = function(element){ var node = new Node(element),      current; //操作所用指针 if (!head){ head = node; }else { current = head; while(current.next){ current = current.next; } current.next = node; } length++; return true;};this.insert = function(position, element){ if (position >= 0 && position <= length) { var node = new Node(element), current = head, previous, index = 0; if(position === 0){ node.next = current; head = node; }else{ while(index++ < position){ previous = current; current = current.next; } node.next = current; previous.next = node; } length++; return true; }else{ return false; } };this.removeAt = function(position){ if(position > -1 && position < length){ var current = head,     previous,     index = 0; if (position === 0) { head = current.next; }else{ while (index++ < position){ previous = current; current = current.next; } previous.next = current.next; }; length--; return current.element; }else{ return null; }};this.remove = function(element){ var current = head,     previous; if(element === current.element){ head = current.next; length--; return true; } previous = current; current = current.next; while(current){ if(element === current.element){ previous.next = current.next; length--; return true; }else{ previous = current; current = current.next; } } return false;};this.remove = function(){ if(length < 1){ return false; } var current = head, previous; if(length == 1){ head = null; length--; return current.element; }  while(current.next !== null){ previous = current; current = current.next; } previous.next = null; length--; return current.element;};this.indexOf = function(element){ var current = head,     index = 0; while(current){ if(element === current.element){ return index; } index++; current = current.next; } return false;};this.isEmpty = function(){ return length === 0;};this.size = function(){ return length;};this.toString = function(){ var current = head,     string = ''; while(current){ string += current.element; current = current.next; } return string;}; this.getHead = function(){ return head;}}

循环链表：在单链表的基础上，将尾节点的指针指向头结点，就构成了一个循环链表。环形链表从任意一个节点开始，都可以遍历整个链表。

function CircularLinkedList(){var Node = function(element){this.element = element;this.next = null;}var length = 0,    head   = null;this.append = function(element){var node = new Node(element),    current;if (!head) {head = node;node.next = head;}else{current = head;while(current.next !== head){current = current.next;}current.next = node;node.next = head;};length++;return true;};this.insert = function(position, element){if(position > -1 && position < length){var node = new Node(element),    index = 0,    current = head,    previous;if (position === 0) {node.next = head;head = node;}else{while(index++ < position){previous = current;current = current.next;}previous.next = node;node.next = current;};length++;return true;}else{return false;}};this.removeAt = function(position){if(position > -1 && position < length){ var current = head,     previous,     index = 0; if (position === 0) { head = current.next; }else{ while (index++ < position){ previous = current; current = current.next; } previous.next = current.next; }; length--; return current.element; }else{ return null; }};this.remove = function (element){var current = head,    previous,    indexCheck = 0;while(current && indexCheck < length){if(current.element === element){if(indexCheck == 0){head = current.next;length--;return true;}else{previous.next = current.next;length--;return true;}}else{previous = current;current = current.next;indexCheck++;}}return false;};this.remove = function(){if(length === 0){return false;}var current = head,    previous,    indexCheck = 0;if(length === 1){head = null;length--;return current.element;}while(indexCheck++ < length){previous = current;current = current.next;}previous.next = head;length--;return current.element;};this.indexOf = function(element){var current = head,    index = 0;while(current && index < length){if(current.element === element){return index;}else{index++;current = current.next;}}return false;};this.isEmpty = function(){ return length === 0;};this.size = function(){ return length;};this.toString = function(){ var current = head,     string = '',     indexCheck = 0; while(current && indexCheck < length){ string += current.element; current = current.next; indexCheck++; } return string;}; }

使用方法：

        

在类外部扩充方法：

  

关于双向链表与双向循环链表，见本人另一篇博客：  双向链表、双向循环链表的JS实现

对于链表的封装，完整版地址：https://github.com/zhuwq585/Data-Structure-in-JavaScript/blob/master/LinkedList.js