代码源自《数据结构与算法分析——c语言描述》

二叉查找树的基本操作：

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

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

struct TreeNode
{
    int data;
    SearchTree Left;
    SearchTree Right;
};

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

Position Find(int x, SearchTree T)
{
    if (T == NULL)
        return NULL;
    else if (x < T->data)
        return Find(x, T->Left);
    else if (x > T->data)
        return Find(x, T->Right);
    else
        return T;
}

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

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

SearchTree Insert(int x, SearchTree T)
{
    if (T == NULL)
    {
        //创造并返回一个单节点的树
        T = (SearchTree)malloc(sizeof(struct TreeNode));
        if (T == NULL)
        {
            printf("out of space!");
            exit(1);
        }
        else
        {
            T->data = x;
            T->Left = T->Right = NULL;
        }
    }
    else
        if (x < T->data)
            T->Left=Insert(x, T->Left);
        else
            if (x > T->data)
                T->Right=Insert(x, T->Right);

    return T;
}
SearchTree Delete(int x, SearchTree T)
{
    Position Tmpcell;
    if (T == NULL)
    {
        printf("element not found!\n");
        system("pause");
        exit(1);
    }
    else
        if (x < T->data)
            T->Left = Delete(x, T->Left);
        else
            if (x > T->data)
                T->Right = Delete(x, T->Left);
            else
                if (T->Left&&T->Right)//有两个子树（双分支）
                {
                    //将右子树中最小的元素替换当前节点
                    //实际上没有删除当前节点，而是改变其值为右子树中最小的值，并将该最小值节点删除
                    Tmpcell = FindMin(T->Right);
                    T->data = Tmpcell->data;
                    T->Right = Delete(T->data, T->Right);
                }
                else//一个或无子树
                {
                    Tmpcell = T;
                    if (T->Left == NULL)
                        T = T->Right;
                    else if(T->Right == NULL)
                        T = T->Left;
                    free(Tmpcell);
                }
    return T;
}

void PrintElement(Position p)
{
    printf("%d\t", p->data);
}

void PrintTree(SearchTree T)
{
    if (T != NULL)
    {
        PrintTree(T->Left);
        PrintElement(T);
        PrintTree(T->Right);
    }
}

功能测试：

int main()
{
    SearchTree tree;
    tree = NULL;
    int temp;
    char c;
    do
    {
        printf("enter :\n");
        scanf("%c", &c);
        switch (c)
        {
        case ('i'):
            printf("please enter a num you want to insert:");
            scanf("%d", &temp);
            tree=Insert(temp, tree);
            while ((c = getchar()) != '\n')
                scanf("%c", &c);
            break;
        case ('d'):
            printf("please enter a num you want to delete:");
            scanf("%d", &temp);
            tree=Delete(temp, tree);
            while ((c = getchar()) != '\n')
                scanf("%c", &c);
            break;
        case('s'):
            printf("we are goning to show you the data after sorted:\n");
            PrintTree(tree);
            while ((c = getchar()) != '\n')
                scanf("%c", &c);
        };
    } while (c != 'e');

    system("pause");
    return 0;
}

avl树的旋转：