二叉搜索树实现

BinarySearchTree

#include<stdlib.h>
#include<malloc.h>
#include<stdio.h>

struct TreeNode;
typedef struct TreeNode *Position;
typedef struct TreeNode *SearchTree;
typedef char ElementType;

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);

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

/* Routine to make an empty tree */
SearchTree MakeEmpty(SearchTree T) {
    if (T != NULL) {
        MakeEmpty(T->Left);
        MakeEmpty(T->Right);
        free(T);
    }
    return NULL;
}

/* Find operation for binary search trees */
Position Find(ElementType X, SearchTree T) {
    if (T == NULL)
        return NULL;
    if (X < T->Element)
        return Find(X, T->Left);
    else if (X > T->Element)
        return Find(X, T->Right);
    else
        return T;
}

/* Recursive implementation of FindMin for biany search trees */
Position FindMin(SearchTree T) {
    if (T == NULL)
        return NULL;
    else if (T->Left == NULL)
        return T;
    else
        return FindMin(T->Left);
}

/* Nonrecursive implementation of FindMax for binary search trees */
Position FindMax(SearchTree T) {
    if (T != NULL)
        while (T->Right != NULL)
            T = T->Right;
    return T;
}

/* Insertion into a binary search tree */
SearchTree Insert(ElementType X, SearchTree T) {
    if (T == NULL) {
        /* Create and return a one-node tree */
        T = (SearchTree) malloc(sizeof(TreeNode));
        if (T == NULL)
            printf("Out of space !");
        else {
            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;
}

/* Deletion routinue for binary search tree */
SearchTree Delete(ElementType X, SearchTree T) {
    Position TmpCell;

    if (T == NULL)
        printf("Element not found");
    else if (X < T->Element) /* Go left */
        T->Left = Delete(X, T->Left);
    else if (X > T->Element) /* Go right  */
        T->Right = Delete(X, T->Right);
    else if (T->Left && T->Right) {
        /* Replace with smallest in right subtree */
        TmpCell = FindMin(T->Right);
        T->Element = TmpCell->Element;
        T->Right = Delete(T->Element, T->Right);
    } else { /* One or zero children */
        TmpCell = T;
        if (T->Left == NULL)
            T = T->Right; /* Also handles 0 children */
        else if (T->Right == NULL)
            T = T->Left;
        free(TmpCell);
    }
    return T;
}