JavaScript数据结构之单链表和循环链表

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。  现在就来填坑了奋斗   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：

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：