数据结构--单向链表

单向链表

此案例的插入是每次从头部插入新节点，所以遍历时，数据从新到旧

package cn.itcast.entity;

public class Node

{

   public int i ;

   public Node next ;

}

-------------------------------------

package cn.itcast.entity;

public class NodeList

{

   private Node first ;//要插入的新节点

   private Node front ;//指向当前节点的前面一个变量

   private Node current ;//指向当前节点

   //添加新节点

   public void insert ( int i )

   {

      //如果first 为空，代表第一次插入数据，直接向first里放入数据

      if ( first == null )

      {

         first = new Node () ;

         first.i = i ;

      }

      //不为空，说明有数据了，这里我们用从头部插入的方式，即新node为first，老first指向新node.next

      else

      {

         Node newNode = new Node ();

         newNode.i = i ;

         newNode.next = first ;

         first = newNode ;

      }

   }

   //按内容删除

   public void delete ( int i )

   {

      //使用current来遍历链表以查找元素

      current = first ;

      front = first ;

      while ( current != null )

      {

         //如果不等于，代表没找到要删除的节点

         if ( current.i != i )

         {

           front = current ;

           current = current.next ;

         }

         //否则，代表找到要删除的节点

         else

         {

           //将要删除的节点的前一项的next指向要删除节点的next

           front.next = current.next ;

           System.out.println ( "已删除" );

           return ;

         }

      }

      //跳出循环，代表遍历到底了，没有匹配的数据

      System.out.println ( "没找到" );

      return ;

   }

   //按序号修改

   public void update ( int i , int data )

   {

      //序号

      int count = 1 ;

      current = first ;

      //遍历寻找序号符合的

      while ( current != null )

      {

         //找到了

         if ( count == i )

         {

           current.i = data ;

           return ;

         }

         //没找到

         current = current.next ;

         count ++ ;

      }

      //跳出循环，代表输入的序号超出当前最大值

      System.out.println ( "超出链表长度" );

   }

   //按内容查找

   public Node findByData ( int i )

   {

      current = first ;

      //循环遍历

      while ( current != null )

      {

         //找到就将当前节点返回

         if ( current.i == i )

         {

           return current ;

         }

         //没找到，就继续下一个

         current = current.next ;

      }

      //循环结束，说明到底了

      System.out.println ( "没找到" );

      return null ;

   }

   //链表长度

   public int length ()

   {

      //统计个数

      int count = 0 ;

      current = first ;

      //遍历中统计个数

      while ( current != null )

      {

         ++ count ;

         current = current.next ;

      }

      return count  ;

   }

   //遍历

   public void display ()

   {

      current = first ;

      while ( current != null )

      {

         System.out.print ( current.i + "," );

         current = current.next ;

      }

      System.out.println (  );

   }

}

-------------------------------------------

package cn.itcast.entity;

import org.junit.Test;

public class test

{

   @Test

   public void t ()

   {

      NodeList nl = new NodeList () ;

      nl.insert ( 1 );

      nl.insert ( 2 );

      nl.insert ( 3 );

      nl.insert ( 4 );

      nl.insert ( 5 );

      nl.insert ( 6 );

      nl.display ();

      System.out.println ( nl.length () );

      nl.delete ( 1 );

      nl.display ();

      System.out.println ( nl.length () );

      nl.update ( 6 , 1 );

      nl.display ();

      System.out.println ( nl.length () );

      System.out.println ( nl.findByData ( 6 ).i );

   }

}

-------------------------------运行结果--------------------

6,5,4,3,2,1,

6

已删除

6,5,4,3,2,

5

超出链表长度

6,5,4,3,2,

5

6