curriculum/challenges/english/blocks/learn-tree-traversal-by-building-a-binary-search-tree/65ca071d5921760254949f76.md
The conditionals you wrote in the previous steps are valid for nodes with either zero or one child. The upcoming conditionals will be valid if there are 2 children.
For that, add an else clause to the conditional.
You should add an else clause. Remember to use the pass keyword.
({ test: () => assert(runPython(`_Node(_code).find_class("BinarySearchTree").find_function("_delete").find_ifs()[1].find_conditions()[2].tree is None`)) })
class TreeNode:
def __init__(self, key):
self.key = key
self.left = None
self.right = None
def __str__(self):
return str(self.key)
class BinarySearchTree:
def __init__(self):
self.root = None
def _insert(self, node, key):
if node is None:
return TreeNode(key)
if key < node.key:
node.left = self._insert(node.left, key)
elif key > node.key:
node.right = self._insert(node.right, key)
return node
def insert(self, key):
self.root = self._insert(self.root, key)
def _search(self, node, key):
if node is None or node.key == key:
return node
if key < node.key:
return self._search(node.left, key)
return self._search(node.right, key)
def search(self, key):
return self._search(self.root, key)
--fcc-editable-region--
def _delete(self, node, key):
if node is None:
return node
if key < node.key:
node.left = self._delete(node.left, key)
elif key > node.key:
node.right = self._delete(node.right, key)
--fcc-editable-region--
bst = BinarySearchTree()
nodes = [50, 30, 20, 40, 70, 60, 80]
for node in nodes:
bst.insert(node)
# print('Search for 80:', bst.search(80))