有了上一篇的二级指针优化，平衡二叉树的左旋，右旋，左平衡和右平衡就会简单一些。强烈建议你先看一下：
http://blog.csdn.net/wsrspirit/article/details/51374117
目前代码只有创建，删除还没有加入。没有注释，不好意思。你可以找其他的博客了解~C实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LH 1
#define EH 0
#define RH -1


typedef struct tree_struct
{
    int value;
    int balance;
    struct tree_struct *lchild;
    struct tree_struct *rchild;
}tree_t;


void for_each(tree_t *bs_tree)
{
    if (bs_tree != NULL)
    {
        printf("value %d balance %d\n", bs_tree->value,bs_tree->balance);
        for_each(bs_tree->lchild);
        for_each(bs_tree->rchild);
    }
}


void right_rotate(tree_t **root)
{
    tree_t *lchild = (*root)->lchild;
    (*root)->lchild = lchild->rchild;
    lchild->rchild = (*root);
    (*root) = lchild;
}

void left_rotate(tree_t **root)
{
    tree_t *rchild = (*root)->rchild;
    (*root)->rchild = rchild->lchild;
    rchild->lchild = (*root);
    (*root) = rchild;
}


void left_balance(tree_t **root)
{
    tree_t *lchild = (*root)->lchild;
    tree_t *lr = lchild->rchild;

    switch(lchild->balance)
    {
        case LH:
            (*root)->balance = lchild->balance = EH;
            right_rotate(root);
        break;
        case RH:
            switch(lr->balance)
            {
                case LH:
                    lchild->balance = EH;
                    (*root)->balance = RH;
                break;
                case EH:
                    lchild->balance = (*root)->balance = EH;
                break;
                case RH:
                    lchild->balance = LH;
                    (*root)->balance = EH;
                break;
            }
            lr->balance = EH;
            // printf("before left_rotate\n");
            // for_each(*root);
            left_rotate(&(*root)->lchild); // printf("before right_rotate\n"); // for_each(*root); right_rotate(root); } } void right_balance(tree_t **root) { tree_t *rchild = (*root)->rchild;
    tree_t *rl = rchild->lchild;

    switch(rchild->balance)
    {
        case RH:
            (*root)->balance = rchild->balance = EH;
            left_rotate(root);
        break;
        case LH:
            switch(rl->balance)
            {
                case RH:
                    rchild->balance = EH;
                    (*root)->balance = LH;
                break;
                case EH:
                    rchild->balance = (*root)->balance = EH;
                break;
                case LH:
                    rchild->balance = RH;
                    (*root)->balance = EH;
                break;
            }
            rl->balance = EH;
            // printf("before left_rotate\n");
            // for_each(*root);
            right_rotate(&(*root)->rchild); // printf("before right_rotate\n"); // for_each(*root); left_rotate(root); } } int insert_val(tree_t **root,int key,int *taller) { if (!(*root)) { *root = malloc(sizeof(tree_t)); (*root)->balance = EH;
        (*root)->lchild = (*root)->rchild = NULL;
        (*root)->value = key;
        *taller = 1;
        return 1;
    }
    else
    {
        if ((*root)->value == key) { *taller = 0; return 0; } else { if ((*root)->value > key) { if(insert_val(&(*root)->lchild,key,taller)) { if (*taller) { switch((*root)->balance) { case LH: printf("ll\n"); left_balance(root); *taller = 0; break; case EH: printf("le\n"); (*root)->balance = LH;
                                *taller = 1;
                            break;
                            case RH:
                                printf("lr\n");
                                (*root)->balance = EH;
                                *taller = 0;
                            break;
                        }
                    }

                    return 1;
                }
                else
                    return 0;
            }
            else
            {
                if(insert_val(&(*root)->rchild,key,taller)) { if (*taller) { switch((*root)->balance) { case LH: printf("rl\n"); (*root)->balance = EH;
                                *taller = 0;
                            break;
                            case EH:
                                printf("re\n");
                                (*root)->balance = RH;
                                *taller = 1;
                            break;
                            case RH:
                                printf("rr\n");
                                right_balance(root);
                                *taller = 0;
                            break;
                        }
                    }
                    return 1;
                }
                else
                    return 0;
            }
        }
    }
}

void init_val(int *a,int n,tree_t **avl_tree)
{
    int i = 0;
    int taller;
    while(i < n)
    {
        insert_val(avl_tree,a[i],&taller);
        i++;
    }
}

int main(int argc, char const *argv[])
{
    int a[10] = {62,70,20,65,66,80,30,25,87,50};
    tree_t *avl_tree;
    avl_tree = NULL;
    init_val(a,10,&avl_tree);
    printf("after\n");
    for_each(avl_tree);
    return 0;
}

代码下载：
http://download.csdn.net/detail/wsrspirit/9519288