/* also fixes height */
static void
avlRebalance(AvlTree *t)
{
int d;
if (*t != AVL_EMPTY) {
for (d = 0; d < 2; d++) {
/* maybe child[d] is now too tall */
if (avlGetHeight((*t)->child[d]) > avlGetHeight((*t)->child[!d]) + 1) {
/* imbalanced! */
/* how to fix it? */
/* need to look for taller grandchild of child[d] */
if (avlGetHeight((*t)->child[d]->child[d]) > avlGetHeight((*t)->child[d]->child[!d])) {
/* same direction grandchild wins, do single rotation */
avlRotate(t, d);
}
else {
/* opposite direction grandchild moves up, do double rotation */
avlRotate(&(*t)->child[d], !d);
avlRotate(t, d);
}
return; /* avlRotate called avlFixHeight */
}
}
/* update height */
avlFixHeight(*t);
}
}
/*
* After an insertion, possibly rebalance the tree so that the left and right
* node heights don't differ by more than 1.
* May update *node.
*/
static void
avlAdjustBalance(avl_tree *tree, avl_node **node)
{
avl_node *current = *node;
int b = avlBalance(current) / 2;
if (b != 0)
{
int dir = (1 - b) / 2;
if (avlBalance(current->children[dir]) == -b)
avlRotate(¤t->children[dir], !dir);
current = avlRotate(node, dir);
}
if (current != tree->end)
avlUpdateHeight(current);
}