# we need to check the parent
# we may be the left child, thus we need to return parent
# we may be the right child, we need to go to grandpa
while node.parent and node.parent.nodes[0] != node:
node = node.parent
return node.parent
bt = BinaryTree(BinaryTree.build((8, [(4, [2, 6]), (10, [None, 20])])))
for use_case, expected_result in [
(4, 6),
(6, 8),
(10, 20),
(20, None),
]:
node = bt.find_node(use_case)
result = find_successor(node)
if not expected_result:
assert result is None, "{} is not None".format(result)
else:
if result is None:
assert False, "None != {}".format(expected_result)
else:
assert result.val == expected_result, "{} != {}".format(
result, expected_result)
