二叉查找树ADT--C语言描述

首先给出此ADT的声明：

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

 SearchTree MakeEmpty(SearchTree T);
 Position Find(ElementType X, SearchTree T);
 Position FindMax(SearchTree T);
 Position FindMin(SearchTree T);
 SearchTree Insert(ElementType X, SearchTree T);
 SearchTree Delete(ElementType X, SearchTree T);
 ElementType Retrieve(Position P);

 struct TreeNode{
     ElementType Element;
     SearchTree Left;
     SearchTree Right;
 };

1、MakeEmpty的实现

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

2、Find的实现

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

3、FindMax和FindMin的实现（一个递归 一个非递归）

Position FindMin(SearchTree T){
    if(T == NULL)
        return NULL;
    else if(T->Left == NULL)
        return T;
    else
        return FindMin(T->Left);
}

Position FindMax(SearchTree T){
    if(T != NULL)
        while(T->Right != NULL)
            T = T->Right;
    return T;
}

4、Insert的实现

 SearchTree Insert(ElementType X, SearchTree T){
     if(T == NULL){
         T = (SearchTree)malloc(sizeof(struct TreeNode));
         T->Element = X;
         T->Left = 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);

     // Else X is in the tree already, we'll do nothing!
     return T;
 }

5、Delete的实现

 SearchTree Delete(ElementType X, SearchTree T){
     Position TmpCell;

     if(T == NULL)
         printf("Element Not Found\n");
     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 && T->Right){
         TmpCell = FindMin(T->Right);
         T->Element = TmpCell->Element;
         T->Right = Delete(TmpCell->Element, T->Right);
     }
     else{
         TmpCell = T;
         if(!(T->Left))
             T = T->Right;
         else if(!(T->Right))
             T = T->Left;
         free(TmpCell);
     }
     return T;
 }