def test_preorder_full(self):
tree = TreeNode(
4,
left=TreeNode(1, right=TreeNode(2)),
right=TreeNode(7, left=TreeNode(5), right=TreeNode(8))
)
self.assertEqual(preorder_walk(tree), [4, 1, 2, 7, 5, 8])
def test_preorder_two(self):
tree = TreeNode(
4,
TreeNode(1)
)
self.assertEqual(preorder_walk(tree), [4, 1])
def test_preorder_single(self):
tree = TreeNode(4)
self.assertEqual(preorder_walk(tree), [4])
