static bs_tree_node_t* delete_node(bs_tree_t* tree, bs_tree_node_t* node, void* key)
{
int cmp = tree->compare(node->key, key);
if(cmp < 0)
{
if(node->left) delete_node(tree, node->left, key);
else return NULL;
}
else if(cmp > 0)
{
if(node->right) delete_node(tree, node->right, key);
else return NULL;
}
else
{
if(node->left && node->right)
{
bs_tree_node_t* successor = find_min(node->right);
swap_nodes(successor, node);
replace_node_in_parent(tree, successor, successor->right);
return successor;
}
else if(node->left) replace_node_in_parent(tree, node, node->left);
else if(node->right) replace_node_in_parent(tree, node, node->right);
else replace_node_in_parent(tree, node, NULL);
return node;
}
}
void BST<T>::erase(iterator itr) {
--cnt;
if( cnt == 0 ) {
delete root;
root = nullptr;
return;
}
// if left & right child both exist
if( (itr.node)->left && (itr.node)->right ) {
TreeNode<T> *predecessor = findMax((itr.node)->left);
(itr.node)->val = predecessor->val;
erase(iterator(predecessor));
// if only left child exist
} else {
TreeNode<T> *child = (itr.node)->left ? (itr.node)->left : (itr.node)->right;
replace_node_in_parent(itr.node, child);
delete itr.node;
}
}
