static caddr_t
ravl_delete(
Avlnode **root,
caddr_t data,
IFP fcmp,
int *shorter
)
{
int shortersubtree = 0;
int cmp;
caddr_t savedata;
Avlnode *minnode, *savenode;
if ( *root == NULLAVL )
return( 0 );
cmp = (*fcmp)( data, (*root)->avl_data );
/* found it! */
if ( cmp == 0 ) {
savenode = *root;
savedata = savenode->avl_data;
/* simple cases: no left child */
if ( (*root)->avl_left == 0 ) {
*root = (*root)->avl_right;
*shorter = 1;
free( (char *) savenode );
return( savedata );
/* no right child */
} else if ( (*root)->avl_right == 0 ) {
*root = (*root)->avl_left;
*shorter = 1;
free( (char *) savenode );
return( savedata );
}
/*
* avl_getmin will return to us the smallest node greater
* than the one we are trying to delete. deleting this node
* from the right subtree is guaranteed to end in one of the
* simple cases above.
*/
minnode = (*root)->avl_right;
while ( minnode->avl_left != NULLAVL )
minnode = minnode->avl_left;
/* swap the data */
(*root)->avl_data = minnode->avl_data;
minnode->avl_data = savedata;
savedata = ravl_delete( &(*root)->avl_right, data, fcmp,
&shortersubtree );
if ( shortersubtree )
*shorter = right_balance( root );
else
*shorter = 0;
/* go left */
} else if ( cmp < 0 ) {
if ( (savedata = ravl_delete( &(*root)->avl_left, data, fcmp,
&shortersubtree )) == 0 ) {
*shorter = 0;
return( 0 );
}
/* left subtree shorter? */
if ( shortersubtree )
*shorter = left_balance( root );
else
*shorter = 0;
/* go right */
} else {
if ( (savedata = ravl_delete( &(*root)->avl_right, data, fcmp,
&shortersubtree )) == 0 ) {
*shorter = 0;
return( 0 );
}
if ( shortersubtree )
*shorter = right_balance( root );
else
*shorter = 0;
}
return( savedata );
}
/*
* 插入结点到AVL树
*
* 结点已存在，返回0；出错，返回-1，成功返回1
*/
int
insert_avl(struct avl **tree, int item, int *taller)
{
int ret = 0;
if (*tree == NULL) {
/* 树为空，插入为根结点 */
*tree = (struct avl *) malloc(sizeof(struct avl));
if (*tree == NULL)
return -1;
(*tree)->data = item;
(*tree)->lchild = (*tree)->rchild = NULL;
(*tree)->bf = EH;
*taller = 1; /* 树长高了 */
} else {
/* 结点已经存在 */
if (item == (*tree)->data) {
*taller = 0;
return 0;
}
/* 结点小于根结点，往左子树查找，递归 */
if (item < (*tree)->data) {
ret = insert_avl(&(*tree)->lchild, item, taller);
if (ret != 1) /* 未插入 */
return ret;
/* 新插入结点到左子树，且左子树长高了 */
if (*taller == 1) {
/* 检查树的平衡度 */
switch ((*tree)->bf) {
case LH:
/* 插入结点后，左子树比右子树高，作左平衡处理 */
left_balance(tree);
*taller = 0;
break;
case EH:
/* 原本左右子树等高，插入新结点后，根增高 */
(*tree)->bf = LH;
*taller = 1;
break;
case RH:
/* 原本右子树比左子树高，插入后等高 */
(*tree)->bf = EH;
*taller = 0;
break;
}
}
/* 结点大于根结点，往右子树查找，递归 */
} else if (item > (*tree)->data) {
ret = insert_avl(&(*tree)->rchild, item, taller);
if (ret != 1) /* 未插入 */
return ret;
/* 新插入结点到右子树，且右子树长高了 */
if (*taller == 1) {
/* 检查树的平衡度 */
switch ((*tree)->bf) {
case LH:
/* 原本左子树比右子树高，插入后等高 */
(*tree)->bf = EH;
*taller = 0;
break;
case EH:
/* 原本左右子树等高，插入结点后，树增高 */
(*tree)->bf = RH;
*taller = 1;
break;
case RH:
/* 插入后右子树比左子树高，作右平衡处理 */
right_balance(tree);
*taller = 0;
break;
}
}
}
}
return 1;
}
