C实现查找二叉树

struct search_tree
{
    struct search_tree *lchild;
    struct search_tree *rchild;
    struct search_tree *parent;

    void *private_data;
};

struct search_tree *make_empty(struct search_tree *T)
{
    if( T != NULL)
    {
        make_empty(T->lchild);
        make_empty(T->rchild);

        free(T);
    }

    return NULL;
}

struct search_tree *find_node(element x, const struct search_tree *T)
{
    const struct search_tree *tmp = T;

    if ( tmp != NULL)
    {
        if( tmp->private_data != x)
        {
            if( x>tmp->private_data )
                tmp = tmp->rchild;
            else
                tmp = tmp->lchild;

            return find(x,tmp);
        }
        else if(tmp->private_data == x)
            return tmp;
        else
            return NULL;
    }

    return NULL;
}

//递归实现
struct search_tree *find_min(const struct search_tree *T)
{
    struct search_tree *tmp = T;

    if(tmp!=NULL)
        if(tmp->lchild != NULL)
            return find_min(tmp->lchild);

    return tmp;
}

//循环实现
struct search_tree *find_min(const struct search_tree *T)
{
    struct search_tree *tmp;

    tmp = T;

    if( T!=NULL)
        while(tmp->lchild != NULL)
            tmp = tmp->lchild;
   
    return tmp;
}

//递归实现
struct search_tree *find_max(cosnt struct search_tree *T)
{
    struct search_tree *tmp;

    tmp = T;
   
    if(tmp != NULL)
        if(tmp->lchild != NULL)
            return find_max(tmp->lchild);

    return tmp;
}

//循环实现
struct search_tree *find_max(const struct search_tree *T)
{
    struct search_tree *tmp;

    tmp = T;

    if(T != NULL)
        while(tmp->rchild != NULL)
            tmp = tmp->rchild;

    return tmp;
}

struct search_tree *insert( element x , const struct search_tree T)
{
    struct search_tree *tmp = T;
    struct search_tree *new_node = (struct search_tree *)malloc(sizeof(struct search_tree));

    new_node -> private_data = x;

    if( T!=NULL && x!=T->private_data )
    {
        if(new_node->private_data > T->private_data)
            tmp = T-> rchild;
        else
            tmp = T->lchild;

        insert(x,tmp);
    }
    else
        tmp = new_node;

    return tmp;
}

int delete( element x, const struct search_tree T)
{
    struct search_tree  *tmp, *del_node, *rpl_node;
    tmp = T;

    if( T != NULL)
    {
        if( (del_node = find_node(element x, const struct search_tree T)) !=NULL )
        {
            if(del_node->rchild != NULL)
            {
                rpl_node = find_min(del_node->rchild);

                rpl_node->parent = del_node->parent;
                rpl_node->lchild = del_node->lchild;

                if(del_node->rchild != rpl_node)
                    del_node->rchild->parent = rpl_node;
                else
                    rpl_node->parent->lchild = NULL;
            }
            else
            {
                del_node->lchild->parent = del_node->parent;
                del_node->lchild = del_node->lchild;
            }

            free(del_node); 
            del_node = NULL;

            return 1;
        }
        else
            return 0;
    }

    return 0;
}