lookup method
See Set.lookup
Implementation
@override
V? lookup(Object? element) {
if (element is! V || _root == null) return null;
AvlNode<V>? x = _root;
int compare = 0;
while (x != null) {
compare = comparator(element, x.object);
if (compare == 0) {
return x.object;
} else if (compare < 0) {
x = x._left;
} else {
x = x._right;
}
}
return null;
}