curriculum/challenges/english/blocks/learn-tree-traversal-by-building-a-binary-search-tree/65ca089e848eca0672b9cd77.md
Now, back to the _delete method, you have to choose the successor, using the _min_value helper function.
Add a _min_value call after your elif block, passing node.right as the argument. Assign it to the current node key.
You should assign self._min_value(node.right) to node.key after your elif block.
({ test: () => (runPython(`
import ast
assign_after_elif = _Node(_code).find_class("BinarySearchTree").find_function("_delete").find_ifs()[1].tree.orelse[0].orelse[1]
assign_code = ast.get_source_segment(_code, assign_after_elif)
assert _Node(assign_code).is_equivalent("node.key = self._min_value(node.right)")`)) })
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)
else:
if node.left is None:
return node.right
elif node.right is None:
return node.left
--fcc-editable-region--
def _min_value(self, node):
while node.left is not None:
node = node.left
return node.key
bst = BinarySearchTree()
nodes = [50, 30, 20, 40, 70, 60, 80]
for node in nodes:
bst.insert(node)
# print('Search for 80:', bst.search(80))