基本数据结构之Binary Search Tree

一、二叉查找树的实现（C）

1）二叉查找树的结点结构

    

typedef struct node

{

     int data ;

     struct node * lchild ;

     struct node * rchild ;

} BSTnode ;

2）创建一个新结点

BSTnode * create_node ( int data )

{

     BSTnode * new_node = ( BSTnode * ) malloc ( sizeof ( BSTnode ));

     if ( new_node == NULL )

     {

         fprintf ( stderr , "Allocate memory error! (create_node) \n " );

         exit ( 1 );

     }

     new_node -> data = data ;

     new_node -> lchild = NULL ;

     new_node -> rchild = NULL ;

     return new_node ;

}

typedefint(*comparer)(int,int);//compare the node value

3）插入一个

BSTnode * insert_node ( BSTnode * root , comparer compare , int data )

{

 

     if ( root == NULL )

     {

         root = create_node ( data );

     }

     else

     {

         int is_left = 0 ;

         int r = 0 ;

         BSTnode * cursor = root ;

         BSTnode * prev = NULL ;

 

         while ( cursor != NULL )

         {

             r = compare ( data , cursor -> data );

             prev = cursor ;

             if ( r < 0 )

             {

                 is_left = 1 ;

                 cursor = cursor -> lchild ;

             }

             else if ( r > 0 )

             {

                 is_left = 0 ;

                 cursor = cursor -> rchild ;

             }

 

         }

         if ( is_left )

             prev -> lchild = create_node ( data );

         else

             prev -> rchild = create_node ( data );

 

     }

     return root ;

}

4）删除一个结点

     删除一个结点分三种情况：

      1、该结点没有孩子结点

      2、该结点有一个孩子结点

      3、该结点有两个孩子结点

BSTnode * delete_node ( BSTnode * root , int data , comparer compare )

{

     BSTnode * cursor ;

int r = compare ( data , root -> data );

BSTnode * parent = NULL ; if ( root == NULL )

         return NULL ;

 

    

     if ( r < 0 )

         root -> lchild = delete_node ( root -> lchild , data , compare );

     else if ( r > 0 )

         root -> rchild = delete_node ( root -> rchild , data , compare );

     else

     {

         if ( root -> lchild == NULL )

         {

             cursor = root -> rchild ;

             free ( root );

             root = cursor ;

         }

         else if ( root -> rchild == NULL )

         {

             cursor = root -> lchild ;

             free ( root );

             root = cursor ;

         }

         else //2 children

         {

             cursor = root -> rchild ;

            

 

             while ( cursor -> lchild != NULL )

             {

                 parent = cursor ;

                 cursor = cursor -> child ;

             }

             root -> data = cursor -> data ;

             if ( parent != NULL )

                 parent -> lchild = delete_node ( parent -> lchild , parent -> lchild -> data , compare );

             else

                 root -> rchild = delete_node ( root -> rchild , root -> rchild -> data , compare );

         }

     }

     return root ;

}

5）查找一个结点

BSTnode * search ( BSTnode * root , const int data , comparer compare )

{

     int r ;

     BSTnode * cursor = root ;

if ( root == NULL )

         return NULL ;

 

     while ( cursor != NULL )

     {

         r = compare ( data , cursor -> data );

         if ( r < 0 )

             cursor = cursor -> lchild ;

         else if ( r > 0 )

             cursor = cursor -> rchild ;

         else

             return cursor ;

     }

     return cursor ;

}

6）遍历这课BST

typedefvoid(*callback)(BSTnode*);

void traverse ( BSTnode * root , callback cb )

{

     BSTnode * cursor , * pre ;

 

     if ( root == NULL )

         return ;

 

     cursor = root ;

 

     while ( cursor != NULL )

     {

         if ( cursor -> lchild != NULL )

         {

             cb ( cursor );

             cursor = cursor -> rchild ;

         }

         else

         {

             pre = cursor -> lchild ;

 

             while ( pre -> rchild != NULL && pre -> rchild != cursor )

                 pre = pre -> rchild ;

 

             if ( pre -> rchild != NULL )

             {

                 pre -> rchild = cursor ;

                 cursor = cursor -> lchild ;

             }

             else

             {

                 pre -> rchild = NULL ;

                 cb ( cursor );

                 cursor = cursor -> rchild ;

             }

         }

     }

}

7）删除该给定的BST

void dispose ( BSTnode * root )

{

     if ( root != NULL )

     {

         dispose ( root -> lchild );

         dispose ( root -> rchild );

         free ( root );

     }

}

8）显示单个结点的值

void display ( BSTnode * nd )

{

     if ( nd != NULL )

         printf ( "%d " , nd -> data );

}

9）显示整棵树的值

void display_tree ( BSTnode * nd )

{

     if ( nd == NULL )

         return ;

     /* display node data */

     printf ( "%d" , nd -> data );

     if ( nd -> lchild != NULL )

         printf ( "(L:%d)" , nd -> lchild -> data );

     if ( nd -> rchild != NULL )

         printf ( "(R:%d)" , nd -> rchild -> data );

     printf ( " \n " );

 

     display_tree ( nd -> lchild );

     display_tree ( nd -> rchild );

}

/*

compare two integers

*/

int compare ( int left , int right )

{

     if ( left > right )

         return 1 ;

     if ( left < right )

         return - 1 ;

     return 0 ;

}

以上便是BST树的C语言实现。

不明白的可以留言！