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fix tdelete to properly balance the tree

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the tsearch data structure is an avl tree, but it did not implement
the deletion operation correctly so the tree could become unbalanced.

reported by Ed Schouten.
This commit is contained in:
Szabolcs Nagy 2015-12-05 21:02:34 +01:00 committed by Rich Felker
parent 7b712844e3
commit e4f9d81168
1 changed files with 14 additions and 5 deletions
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19
src/search/tsearch_avl.c
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@ -105,10 +105,13 @@ static struct node *insert(struct node **n, const void *k,
return r;
}
static struct node *movr(struct node *n, struct node *r) {
if (!n)
return r;
n->right = movr(n->right, r);
static struct node *remove_rightmost(struct node *n, struct node **rightmost)
{
if (!n->right) {
*rightmost = n;
return n->left;
}
n->right = remove_rightmost(n->right, rightmost);
return balance(n);
}
@ -122,7 +125,13 @@ static struct node *remove(struct node **n, const void *k,
c = cmp(k, (*n)->key);
if (c == 0) {
struct node *r = *n;
*n = movr(r->left, r->right);
if (r->left) {
r->left = remove_rightmost(r->left, n);
(*n)->left = r->left;
(*n)->right = r->right;
*n = balance(*n);
} else
*n = r->right;
free(r);
return parent;
}