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curriculum/challenges/english/blocks/learn-tree-traversal-by-building-a-binary-search-tree/65ca2a18039c942f04ddde83.md

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--description--

Confirm that 40 has been deleted.

Call print() by passing the string 'Search for 40:' as the first argument and an bst.search(40) call as the second argument.

--hints--

You should have print('Search for 40:', bst.search(40)) in your code.

js
({ test: () => assert.match(code, /^print\(\s*("|')Search for 40:("|')\s*,\s*bst\.search\(\s*40\s*\)\s*\)/m) })

--seed--

--seed-contents--

py

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)

    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   
            
            node.key = self._min_value(node.right)
            node.right = self._delete(node.right, node.key)   
        
        return node

    def delete(self, key):
        self.root = self._delete(self.root, key)

    def _min_value(self, node):
        while node.left is not None:
            node = node.left
        return node.key

    def _inorder_traversal(self, node, result):
        if node:
            self._inorder_traversal(node.left, result)
            result.append(node.key)
            self._inorder_traversal(node.right, result)

    def inorder_traversal(self):
        result = []
        self._inorder_traversal(self.root, result)
        return result

--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))

print("Inorder traversal:", bst.inorder_traversal())

bst.delete(40)

--fcc-editable-region--