Skip List, C#实现

温习下数据结构, C#版的Skip List实现

 

Skip List

namespace  Ln.SkipList
{
     ///   <summary>
     ///  the values of list is ascend.
     ///   </summary>
     public   class  SkipList
    {
         private  SkipNode head;
         private  System.Random randomFa  =   new  System.Random();

         public  SkipList(){}
         ///   <summary>
         ///  Initialize skip list
         ///   </summary>
         ///   <returns></returns>
         public   bool  Init()
        {
            head  =   new  SkipNode( 0 ,  null ,  null );
             return   true ;
        }

         ///   <summary>
         ///  Clean skip list
         ///   </summary>
         ///   <returns></returns>
         public   bool  Clear()
        {
            head  =   null ;
             return   true ;
        }

         ///   <summary>
         ///  Insert value to skip list
         ///   </summary>
         ///   <param name="value"></param>
         ///   <returns> if the value exists in the list already, return false. </returns>
         public   bool  Insert( int  value)
        {
             if  (head.nextNode  ==   null )
            {
                SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                head.nextNode  =  newNode;
                 return   true ;
            }

             // check if value existed in the list. check first because prevent duplicated level while raise level.
             if  (Search(value)  ==   true )
            {
                 return   false ;
            }

            SkipNode current  =  head;
             if  (head.nextNode.nextNode  !=   null )
            {
                 // If random > 0.7, raise the hight of level                
                 double  random  =  randomFa.NextDouble();       // get random between 0.0 and 1.0                
                 if  (random  >   0.7 )                
                {
                     // Check vaule if exists in highest level
                    current  =  head.nextNode;
                     while  (current  !=   null )
                    {
                         if  (value  ==  current.value)
                        {
                             return   false ;
                        }
                        current  =  current.nextNode;
                    }

                    current  =  head;

                     if  (head.nextNode.value  <  value)
                    {
                        SkipNode newNode  =   new  SkipNode(head.nextNode.value,  null ,  null );
                        newNode.downNode  =  head.nextNode;
                        head.nextNode  =  newNode;
                        newNode.nextNode  =   new  SkipNode(value,  null ,  null );
                    }
                     else
                    {
                        SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                        newNode.nextNode  =   new  SkipNode(head.nextNode.value,  null ,  null );
                        newNode.nextNode.downNode  =  head.nextNode;
                        head.nextNode  =  newNode;
                    }

                     // If value insert to the first note of list
                     if  (head.nextNode.value  ==  value)
                    {
                        current  =  head.nextNode;
                         while  (current.nextNode.downNode  !=   null )
                        {
                            SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                            newNode.nextNode  =  current.nextNode.downNode;
                            current.downNode  =  newNode;
                            current  =  current.downNode;
                        }
                         return   true ;
                    }

                    current  =  head.nextNode.downNode;
                    SkipNode upNode  =  head.nextNode.nextNode;
                     do
                    {
                         while  (current.nextNode  !=   null   &&  value  >  current.nextNode.value)
                        {
                            current  =  current.nextNode;
                        }
                         if  (current.nextNode  !=   null   &&  value  ==  current.nextNode.value)
                        {
                            upNode.downNode  =  current.nextNode;
                             return   false ;
                        }
                        SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                        upNode.downNode  =  newNode;
                        upNode  =  newNode;
                        newNode.nextNode  =  current.nextNode;
                        current.nextNode  =  newNode;
                        current  =  current.downNode;
                    }  while  (current  !=   null );

                     return   true ;
                }
            }

            current  =  head;
             do
            {
                 while  (current.nextNode  !=   null   &&  value  >  current.nextNode.value)
                {
                    current  =  current.nextNode;
                }
                 if  (current.nextNode  !=   null   &&  value  ==  current.nextNode.value)
                {
                     return   false ;
                }
                 // insert in the lowest level
                 if  (current.downNode  ==   null )
                {
                    SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                    newNode.nextNode  =  current.nextNode;
                    current.nextNode  =  newNode;
                     return   true ;
                }

                 // while gap>3, insert in current and lower level
                 if  (current.downNode.nextNode  !=   null   &&  current.downNode.nextNode.nextNode  !=   null   &&  value  >  current.downNode.nextNode.nextNode.value)
                {
                    SkipNode rootNode  =   new  SkipNode(value,  null ,  null );
                    rootNode.nextNode  =  current.nextNode;
                    current.nextNode  =  rootNode;
                    current  =  current.downNode.nextNode.nextNode;
                     while  (current  !=   null )
                    {
                         while  (current.nextNode  !=   null   &&  value  >  current.nextNode.value)
                        {
                            current  =  current.nextNode;
                        }
                         if  (current.nextNode  !=   null   &&  value  ==  current.nextNode.value)
                        {
                             return   false ;
                        }
                        SkipNode newNode  =   new  SkipNode(value,  null ,  null );
                        rootNode.downNode  =  newNode;
                        rootNode  =  newNode;
                        newNode.nextNode  =  current.nextNode;
                        current.nextNode  =  newNode;
                        current  =  current.downNode;
                    }
                     return   true ;
                }
                current  =  current.downNode;
            }  while  (current  !=   null );

             return   true ;
        }

         public   bool  Search( int  value)
        {
             if  (head.nextNode  ==   null )
            {
                 return   false ;
            }

            SkipNode current  =  head;
             do
            {
                 while  (current.nextNode  !=   null   &&  value  >  current.nextNode.value)
                {
                    current  =  current.nextNode;
                }
                 if  (current.nextNode  !=   null   &&  value  ==  current.nextNode.value)
                {
                     return   true ;
                }
                current  =  current.downNode;
            }  while  (current  !=   null );
             return   false ;
        }

         public   bool  Remove( int  value)
        {
             if  (head.nextNode  ==   null )
            {
                 return   false ;
            }
            SkipNode current  =  head;
             do  
            {
                 while  (current.nextNode  !=   null   &&  value  >  current.nextNode.value)
                {
                    current  =  current.nextNode;
                }
                 if  (current.nextNode  !=   null   &&  value  ==  current.nextNode.value)
                {
                    current.nextNode  =  current.nextNode.nextNode;
                    current  =  current.downNode;
                     continue ;
                }
                current  =  current.downNode;
            }
             while  (current  !=   null );
             return   true ;
        }

         public   string  Display()
        {
             if  (head.nextNode  ==   null )
            {
                 return   "" ;
            }

            SkipNode current  =  head;
            SkipNode level  =  head.nextNode;
             string  rlt  =   "" ;
             while  (level  !=   null )
            {
                current  =  level;
                 do
                {
                    rlt  +=   " —— "   +  current.value;
                    current  =  current.nextNode;
                }  while  (current  !=   null );
                rlt  +=  System.Environment.NewLine;
                level  =  level.downNode;
            }
             return  rlt;
        }
    }

     class  SkipNode
    {
         public   int  value;
         public  SkipNode downNode;
         public  SkipNode nextNode;

         public  SkipNode()
        {
            value  =   0 ;
            downNode  =   null ;
            nextNode  =   null ;
        }
         public  SkipNode( int  value, SkipNode downNode, SkipNode nextNode)
        {
             this .value  =  value;
             this .downNode  =  downNode;
             this .nextNode  =  nextNode;
        }
    }
}

测试用代码

using  System;
using  System.Collections.Generic;
using  System.Text;
using  Ln.SkipList;

namespace  TestConsoleApplication
{
     class  Program
    {
         static   void  Main( string [] args)
        {
            Random ran  =   new  Random();
            SkipList skipList  =   new  SkipList();
            skipList.Init();
             int  j;
             for  ( int  i  =   0 ; i  <   15 ; i ++ )
            {
                j  =  ran.Next( 0 ,  100 );
                skipList.Insert(j);
                Console.WriteLine(skipList.Search(j));
            }
            Console.WriteLine(skipList.Display());
            Console.ReadLine();
        }
    }
}