/* Remove an element a from the AVL tree t. a must be part of
the tree. Returns True if the depth of the tree has shrunk.
*/
static
Bool avl_remove_wrk ( AvlNode** rootp,
AvlNode* a,
Word(*kCmp)(Word,Word) )
{
Bool ch;
Word cmpres = kCmp( (*rootp)->key, a->key );
if (cmpres > 0) {
/* remove from the left subtree */
AvlNode* left_subtree = (*rootp)->left;
assert(left_subtree);
ch = avl_remove_wrk(&left_subtree, a, kCmp);
(*rootp)->left=left_subtree;
if (ch) {
switch ((*rootp)->balance++) {
case -1:
return True;
case 0:
return False;
case 1:
break;
default:
assert(0);
}
switch ((*rootp)->right->balance) {
case 0:
avl_swl( rootp );
(*rootp)->balance = -1;
(*rootp)->left->balance = 1;
return False;
case 1:
avl_swl( rootp );
(*rootp)->balance = 0;
(*rootp)->left->balance = 0;
return -1;
case -1:
break;
default:
assert(0);
}
avl_swr( &((*rootp)->right) );
avl_swl( rootp );
avl_nasty( *rootp );
return True;
}
}
else if (cmpres < 0) {
/* remove from the right subtree */
AvlNode* right_subtree = (*rootp)->right;
assert(right_subtree);
ch = avl_remove_wrk(&right_subtree, a, kCmp);
(*rootp)->right = right_subtree;
if (ch) {
switch ((*rootp)->balance--) {
case 1:
return True;
case 0:
return False;
case -1:
break;
default:
assert(0);
}
switch ((*rootp)->left->balance) {
case 0:
avl_swr( rootp );
(*rootp)->balance = 1;
(*rootp)->right->balance = -1;
return False;
case -1:
avl_swr( rootp );
(*rootp)->balance = 0;
(*rootp)->right->balance = 0;
return True;
case 1:
break;
default:
assert(0);
}
avl_swl( &((*rootp)->left) );
avl_swr( rootp );
avl_nasty( *rootp );
return True;
}
}
else {
assert(cmpres == 0);
assert((*rootp)==a);
return avl_removeroot_wrk(rootp, kCmp);
}
return 0;
}
/* Remove an element a from the AVL tree t. a must be part of
the tree. Returns True if the depth of the tree has shrunk.
*/
static
Bool avl_remove_wrk ( AvlNode** rootp,
AvlNode* a,
Word(*kCmp)(UWord,UWord) )
{
Bool ch;
Word cmpres;
cmpres = kCmp ? /*boxed*/ kCmp( (*rootp)->key, a->key )
: /*unboxed*/ cmp_unsigned_Words( (UWord)(*rootp)->key,
(UWord)a->key );
if (cmpres > 0){
/* remove from the left subtree */
AvlNode* left_subtree = (*rootp)->child[0];
tl_assert(left_subtree);
ch = avl_remove_wrk(&left_subtree, a, kCmp);
(*rootp)->child[0]=left_subtree;
if (ch) {
switch ((*rootp)->balance++) {
case -1: return True;
case 0: return False;
case 1: break;
default: tl_assert(0);
}
switch ((*rootp)->child[1]->balance) {
case 0:
avl_swl( rootp );
(*rootp)->balance = -1;
(*rootp)->child[0]->balance = 1;
return False;
case 1:
avl_swl( rootp );
(*rootp)->balance = 0;
(*rootp)->child[0]->balance = 0;
return True;
case -1:
break;
default:
tl_assert(0);
}
avl_swr( &((*rootp)->child[1]) );
avl_swl( rootp );
avl_nasty( *rootp );
return True;
}
}
else
if (cmpres < 0) {
/* remove from the right subtree */
AvlNode* right_subtree = (*rootp)->child[1];
tl_assert(right_subtree);
ch = avl_remove_wrk(&right_subtree, a, kCmp);
(*rootp)->child[1] = right_subtree;
if (ch) {
switch ((*rootp)->balance--) {
case 1: return True;
case 0: return False;
case -1: break;
default: tl_assert(0);
}
switch ((*rootp)->child[0]->balance) {
case 0:
avl_swr( rootp );
(*rootp)->balance = 1;
(*rootp)->child[1]->balance = -1;
return False;
case -1:
avl_swr( rootp );
(*rootp)->balance = 0;
(*rootp)->child[1]->balance = 0;
return True;
case 1:
break;
default:
tl_assert(0);
}
avl_swl( &((*rootp)->child[0]) );
avl_swr( rootp );
avl_nasty( *rootp );
return True;
}
}
else {
tl_assert(cmpres == 0);
tl_assert((*rootp)==a);
return avl_removeroot_wrk(rootp, kCmp);
}
return 0;
}
