Learn Tree Traversal by Building a Binary Search Tree - Step 59

Python
1

this is the hint on binary search tree step 59:
You should call the delete method of bst passing 40 as the argument.
now im confused…
hint anyone? :sweat_smile:

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,key):
        self.root = self._insert(self.root, key)

    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 search(self, key):
        return self._search(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 delete(self, key):
        self.root = self._delete(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 _min_value(self, node):
        while node.left is not None:
            node = node.left
        return node.key

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

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


# User Editable Region

bst = BinarySearchTree()
nodes = [50, 30, 20, 40, 70, 60, 80]

for node in nodes:
    bst.insert(node)

print("Inorder traversal:", bst.inorder_traversal())
print("Search for 40:", bst.search(40))
del ???

# User Editable Region

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Challenge Information:

Learn Tree Traversal by Building a Binary Search Tree - Step 59

2

not del, you need to call the method you defined here

1 Like
3

oohh this is the first time ive seen it, I got used to seeing others use the ‘del’
I solved it no worries :grin:

4

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