Learn Tree Traversal by Building a Binary Search Tree - Step 62

Python
1

Tell us what’s happening:

Please I need help in this, I can’t see the errors I’m making here…please I need help

Your code so far


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


# User 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)
yy
print("Search for 40:", bst.search(40))
print('Inorder traversal after deleting 40:',inorder_traversal())

# User Editable Region

Your browser information:

User Agent is: Mozilla/5.0 (iPhone; CPU iPhone OS 16_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/127.0.6533.77 Mobile/15E148 Safari/604.1

Challenge Information:

Learn Tree Traversal by Building a Binary Search Tree - Step 62

1 Like
2

Hi @Osei17,

Look a few lines above the print statement you just added at print("Inorder traversal:", bst.inorder_traversal()). How did you call inorder_traversal() here?

I hope this helps. Happy coding!

2 Likes
3

Please can you give me the structure upon how to get it right, I’m self learner I sometimes struggle with some simple things please.

4

Look at the line that @ablairmorris mentioned, that shows you the correct syntax, line 86.

inorder_traversal() is a Class method and you instantiated the class as bst.

Always look back in your code for clues, especially to do something that you’ve already done.

1 Like