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：

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