二叉查找树

/*接口头文件*/
typedef int ElementType;

#ifndef _SEARCHTREE_H
#define _SEARCHTREE_H

struct TreeNode;
typedef struct TreeNode * PtrToNode;
typedef PtrToNode Position;
typedef PtrToNode SearchTree;

/*操作集*/
SearchTree MakeEmpty( SearchTree T );
Position Find( ElementType X, SearchTree T );
Position FindMin( SearchTree T );
Position FindMax( SearchTree T );
SearchTree Insert( ElementType X, SearchTree T );
SearchTree Delete( ElementType X, SearchTree T );
ElementType Retrieve( Position P );
void PrintfTree( SearchTree T );

#endif 

/*接口实现*/
#include <stdio.h>
#include <stdlib.h>
#include "searchtree.h"

/*特定结构体定义*/
struct TreeNode
{
    ElementType Element;
    SearchTree  Left;
    SearchTree  Right;
};

SearchTree MakeEmpty( SearchTree T )
{
    if ( T != NULL )
    {
        MakeEmpty( T->Left );
        MakeEmpty( T->Right );
        free( T );
    }
    
    return NULL;
}

Position Find( ElementType X, SearchTree T )
{
    if ( T == NULL )
        return NULL;
    
    if ( X < T->Left )
        return Find( X, T->Left );     //尾递归 
    else if ( X > T->Element )
        return Find( X, T->Right );    //尾递归 
    else
        return T;
}

/*递归例程*/ 
Position FindMin( SearchTree T )
{
    if ( T == NULL )
        return NULL;               //No Found
    else if ( T->Left == NULL )    //左子树不存在 
        return T;
    else
        return FindMin( T->Left );
}

/*
  非递归例程 
Position FindMin( SearchTree T )
{
    if ( T != NULL )
        while ( T->Left != NULL )
            T = T->Left;
    
    return T;
}
*/

/*递归例程*/
Position FindMax( SearchTree T )
{
    if ( T == NULL )
        return NULL;
    else if ( T->Right == NULL )
        return T;
    else
        return FindMax( T->Right );
} 

/*
  非递归例程 
Position FindMax( SearchTree T )
{
    if ( T != NULL )
        while ( T->Right != NULL )
            T = T->Right;
    
    return T;
}
*/

SearchTree Insert( ElementType X, SearchTree T )
{
    if ( T == NULL )
    {
        T = ( SearchTree )malloc( sizeof( struct TreeNode ) );
        if ( T == NULL )
        {
            printf( "No Space!!!
" );
            exit( 1 );
        }
        T->Element = X;
        T->Left = NULL;
        T->Right = NULL;
    }
    else if ( X < T->Element )
        T->Left = Insert( X, T->Left );
    else if ( X > T->Element )
        T->Right = Insert( X, T->Right );
    
    return T;
}

SearchTree Delete( ElementType X, SearchTree T )
{
    Position Temp;
    
    if ( T == NULL )
    {
        printf( "No Found!!!
" );
        exit( 1 );
    }
    else if ( X < T->Element )
        T->Left = Delete( X, T->Left );
    else if ( X < T->Element )
        T->Right = Delete( X, T->Right );
    else if ( T->Left != NULL && T->Right != NULL )
    {
        Temp = FindMin( T->Right );
        T->Element = Temp->Element;
        T->Right = Delete( T->Element, T->Right );   
    }
    else
    {
        Temp = T;
        if ( T->Left == NULL )
            T = T->Right;
        else if ( T->Right == NULL )
            T = T->Left;
            
        free( Temp );
    }
    
    return T;
}

void PrintfTree( SearchTree T )
{
    if ( T != NULL )
    {
        PrintfTree( T->Left );
        printf( "%3d", T->Element );
        PrintfTree( T->Right );
    }

}