def test_big(self):
root = TreeNode(
9,
left=TreeNode(8, left=TreeNode(4), right=TreeNode(2)),
right=TreeNode(7, left=TreeNode(6), right=TreeNode(5)),
)
self.assertEqual(root.postorder_traversal(), [4, 2, 8, 6, 5, 7, 9])
def test_root_only(self):
node = TreeNode(77)
self.assertEqual(node.postorder_traversal(), [77])
def test_example(self):
root = TreeNode(4, left=TreeNode("a"), right=TreeNode(7, left=TreeNode(2)))
self.assertEqual(root.postorder_traversal(), ["a", 2, 7, 4])