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curriculum/challenges/english/blocks/learn-tree-traversal-by-building-a-binary-search-tree/65ca085a19adaa057302a3d6.md

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--description--

Inside the while loop body, replace pass with node and assign it the left child of the node.

--hints--

You should remove the pass keyword from the while loop.

js
({
  test: () => {
    const pyClassStr = runPython(
      `str(_Node(_code).find_class("BinarySearchTree").find_function("_min_value"))`
    );
    assert.notInclude(pyClassStr, "pass");
  },
});

You should assign node.left to node inside your while loop.

js
({ test: () => assert.match(code, /node\s*=\s*node\.left/) })

--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    
             
--fcc-editable-region--
    def _min_value(self, node):
        while node.left is not None:
            pass
--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))