伸展树与半伸展树Java实现

伸展树与半伸展树Java实现

伸展树与半伸展树属于自组织的数据结构，能按访问频率调整节点的位置
调整一般通过如下方式：
1）绕根的单旋转，跟AVL的单旋转类似
2）一字型旋转(ZigZig Rotation)
3)之字形旋转(ZigZag Rotation)

旋转操作较简单，有点点繁琐。
半伸展树不做完全的一字型旋转，它只让父节点绕祖父节点做单旋转。

不管怎样，每次访问(插入/查找 ，删除时展开被删除父节点)后把该节点调整到根节点的位置


伸展树代码：

package  algorithms.tree;





/**
 *  @author  yovn
 *
  */
public   class  SplayTree < E  extends  Comparable < E >>   extends  DefaultBSTree < E >   implements  BSTree < E >  {

    
    
     static   class  SplayTreeNode < E  extends  Comparable < E >>   extends  BSTNode < E >
    {

        SplayTreeNode < E >  parent;
        
        SplayTreeNode(SplayTreeNode < E >  parent,E key) {
             super (key);
             this .parent = parent;
            
        
        }
        
    }
    
    
    
    @Override
     public   boolean  delete(E ele) {
           return  _delete((SplayTreeNode < E > )root,ele);
    }



     private   boolean  _delete(SplayTreeNode < E >  pointer, E ele) {
         int  cmp = ele.compareTo(pointer.key);
         while (cmp != 0 )
        {
             if (cmp < 0 )
            {
                pointer = (SplayTreeNode < E > )pointer.left;
            }
             else
            {
                pointer = (SplayTreeNode < E > )pointer.right;
            }
             if (pointer == null ) return   false ;
            cmp = ele.compareTo(pointer.key);
        }
         // okay find it
        SplayTreeNode < E >  p = pointer.parent;
         if (pointer.left == null )
        {
             if (p != null )
            {
                keep_right(pointer);
                splay(p);
            }
             else  {
                root  =  p.right;
                 if (root != null )((SplayTreeNode < E > )root).parent = null ;
            }
            
        }
         else   if (pointer.right == null )
        {
             if (p != null )
            {
                keep_left(pointer);
                splay(p);
            }
             else  {
                root  =  p.left;
                 if (root != null )((SplayTreeNode < E > )root).parent = null ;
            }
        }
         else
        {
            SplayTreeNode < E >  todo = (SplayTreeNode < E > )pointer.left;
            SplayTreeNode < E >  todoP = null ;
             while (todo.right != null )
            {
                todoP = todo;
                todo = (SplayTreeNode < E > )todo.right;
            }
            pointer.key = todo.key;
             if  (todoP  !=   null ) {
                todoP.right  =  todo.left;
                 if  (todo.left  !=   null )
                    ((SplayTreeNode < E > ) todo.left).parent  =  todoP;
            }
             else
            {
                pointer.left = null ;
            }
            splay(pointer.parent);
            
        }
         return   true ;
    }



     private   void  keep_left(SplayTreeNode < E >  pointer) {
        SplayTreeNode < E >  p = pointer.parent;
         if (p.left == pointer)
        {
            p.left = pointer.left;
             if (p.left != null )((SplayTreeNode < E > )p.left).parent = p;
        }
         else   if (p.right == pointer)
        {
            p.right = pointer.left;
             if (p.right != null )((SplayTreeNode < E > )p.right).parent = p;
        }
        
    }



     private   void  keep_right(SplayTreeNode < E >  pointer) {
        SplayTreeNode < E >  p = pointer.parent;
         if (p.left == pointer)
        {
            p.left = pointer.right;
             if (p.left != null )((SplayTreeNode < E > )p.left).parent = p;
        }
         else   if (p.right == pointer)
        {
            p.right = pointer.right;
             if (p.right != null )((SplayTreeNode < E > )p.right).parent = p;
        }
        
    }



    



     protected   void  splay(SplayTreeNode < E >  cur) {
    
         if (cur == null ) return ;
    
         while (cur != root)
        {
             if (cur.parent == root)
            {
                 // single Rotation
                SingleRotation(cur,cur.parent);
                cur.parent = null ;
                root = cur;
            
            }
             else   if (cur.parent.left == cur && cur.parent.parent.left == cur.parent)
            {
                
                cur = Left_ZigZig(cur,cur.parent,cur.parent.parent);
                
            }
             else   if (cur.parent.right == cur && cur.parent.parent.right == cur.parent)
            {
                cur = Right_ZigZig(cur,cur.parent,cur.parent.parent);
            }
             else   if (cur.parent.left == cur && cur.parent.parent.right == cur.parent)
            {
                cur = RL_ZigZag(cur,cur.parent,cur.parent.parent);
            }
             else   if (cur.parent.right == cur && cur.parent.parent.left == cur.parent)
            {
                cur = LR_ZigZag(cur,cur.parent,cur.parent.parent);
            }
             else
            {
                System.out.println( " Oooops!!! " );
            }
        }
    }



     private  SplayTreeNode < E >  LR_ZigZag(SplayTreeNode < E >  cur,
            SplayTreeNode < E >  p, SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        
        g.left = cur.right;
        setParent(cur.right,g);
        
        g.parent = cur;
        cur.right = g;
        
        p.right = cur.left;
        setParent(cur.left,p);
        
        p.parent = cur;
        cur.left = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = cur;
            }
             else
            {
                gp.right = cur;
                
            }
        }
         else  root = cur;
        cur.parent = gp;
         return  cur;
    }



     private  SplayTreeNode < E >  RL_ZigZag(SplayTreeNode < E >  cur,
            SplayTreeNode < E >  p, SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        
        g.right = cur.left;
        setParent(cur.left,g);
        
        g.parent = cur;
        cur.left = g;
        
        p.left = cur.right;
        setParent(cur.right,p);
        
        p.parent = cur;
        cur.right = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = cur;
            }
             else
            {
                gp.right = cur;
                
            }
        }
         else  root = cur;
        cur.parent = gp;
         return  cur;
    }



     protected  SplayTreeNode < E >  Right_ZigZig(SplayTreeNode < E >  cur, SplayTreeNode < E >  p,
            SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        
        g.right = p.left;
        setParent(p.left,g);
        
        
        p.right = cur.left;
        setParent(cur.left,p);
        
        g.parent = p;
        p.left = g;
        
        p.parent = cur;
        cur.left = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = cur;
            }
             else
            {
                gp.right = cur;
                
            }
        }
         else  root = cur;
        cur.parent = gp;
         return  cur;
        
    }



     protected  SplayTreeNode < E >  Left_ZigZig(SplayTreeNode < E >  cur, SplayTreeNode < E >  p,
            SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        g.left = p.right;
        setParent(p.right,g);
        
        g.parent = p;
        p.right = g;
        
        
        p.left = cur.right;
        setParent(cur.right,p);
        
        p.parent = cur;
        cur.right = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = cur;
            }
             else
            {
                gp.right = cur;
                
            }
        }
         else  root = cur;
        cur.parent = gp;
         return  cur;
        
    }



     final   void  setParent(BSTNode < E >  c, BSTNode < E >  p) {
         if (c != null )((SplayTreeNode < E > )c).parent = (SplayTreeNode < E > )p;
        
    }



     private   void  SingleRotation(SplayTreeNode < E >  cur, SplayTreeNode < E >  p) {
         if (p.left == cur)
        {
            
            p.left = cur.right;
             if (cur.right != null )((SplayTreeNode < E > )cur.right).parent = p;
            cur.right = p;
            p.parent = cur;
            
        }
         else   if (p.right == cur)
        {
            p.right = cur.left;
             if (cur.left != null )((SplayTreeNode < E > )cur.left).parent = p;
            cur.left = p;
            p.parent = cur;
            
        }
        
        
    }



    @Override
     public   void  insert(E ele) {

         if  (root  ==   null ) {
            root  =   new  SplayTreeNode < E > ( null ,ele);
             return ;
        }
        _insert((SplayTreeNode < E > )root,ele);
    }
    
     private   final   void  _insert(SplayTreeNode < E >  pointer,E ele)
    {
        
         int  cmp = pointer.key.compareTo(ele);
         if (cmp == 0 )
        {
             throw   new  IllegalArgumentException();
        }
        
         if (cmp > 0 )
        {
             if (pointer.left == null )
            {
                pointer.left  = new  SplayTreeNode < E > (pointer,ele);
                splay((SplayTreeNode < E > )pointer.left);
                 return ;
            }
             _insert((SplayTreeNode < E > )pointer.left,ele);
            
        }
         else
        {
             if (pointer.right == null )
            {
                pointer.right = new  SplayTreeNode < E > (pointer,ele);
                splay((SplayTreeNode < E > )pointer.right);
                 return  ;
            }
            _insert((SplayTreeNode < E > )pointer.right,ele);
        }
    }


    

    @Override
     public   boolean  search(E ele) {
         return  _search((SplayTreeNode < E > )root,ele);
    }

    
     private   boolean  _search(SplayTreeNode < E >  pointer, E ele) {
         if (pointer == null ) return   false ;
         int  cmp = pointer.key.compareTo(ele);
         if (cmp == 0 )
        {
            splay(pointer);
             return   true ;
        }
        
         if (cmp > 0 )
        {
        
            
              return  _search((SplayTreeNode < E > )pointer.left,ele);
            
        }
         else
        {
            
            
             return  _search((SplayTreeNode < E > )pointer.right,ele);
        }
    }


     /**
     * 
      */
     public  SplayTree() {
    
    }

}

半伸展树仅仅改变一下一字旋转时的操作：

package  algorithms.tree;


/**
 *  @author  yovn
 *
  */
public   class  SemiPlayTree < E  extends  Comparable < E >> extends  SplayTree < E >  {

    @Override
     protected  algorithms.tree.SplayTree.SplayTreeNode < E >  Left_ZigZig(
            algorithms.tree.SplayTree.SplayTreeNode < E >  cur,
            algorithms.tree.SplayTree.SplayTreeNode < E >  p,
            algorithms.tree.SplayTree.SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        g.left = p.right;
        setParent(p.right,g);

        p.right = g;
        g.parent = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = p;
            }
             else
            {
                gp.right = p;
                
            }
        }
         else  root = p;
        p.parent = gp;
         return  p;
    }

    @Override
     protected  algorithms.tree.SplayTree.SplayTreeNode < E >  Right_ZigZig(
            algorithms.tree.SplayTree.SplayTreeNode < E >  cur,
            algorithms.tree.SplayTree.SplayTreeNode < E >  p,
            algorithms.tree.SplayTree.SplayTreeNode < E >  g) {
        SplayTreeNode < E >  gp = g.parent;
        g.right = p.left;
        setParent(p.left,g);

        p.left = g;
        g.parent = p;
         if (gp != null )
        {
             if (gp.left == g)
            {
                gp.left = p;
            }
             else
            {
                gp.right = p;
                
            }
        }
         else  root = p;
        p.parent = gp;
         return  p;
    }

    

}