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curriculum/challenges/english/blocks/learn-tree-traversal-by-building-a-binary-search-tree/65c4f3aee69d11dcfdbcfc00.md

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--description--

Now, inside the insert method, you need to call the helper method _insert() that we defined earlier. Here, _insert has encapsulated the implementation of the insertion logic. This is useful for recursion and for keeping the implementation details hidden from the user.

Delete pass and assign self._insert(self.root, key) to self.root.

Note that:

  • self.root passes the root node of the tree as the first argument. This is the starting point for the insertion process.
  • key: passes the key value you want to insert as the second argument.

--hints--

You should remove the pass keyword from the insert method.

js
({
  test: () => {
    assert.isFalse(
      runPython(
        `_Node(_code).find_class("BinarySearchTree").find_function("insert").has_pass()`
      )
    );
  },
});

You should recursively call the _insert() method using self._insert()

js
({ test: () =>
  {
    const transformedCode = code.replace(/\r/g, "");        
    const ins = __helpers.python.getDef("\n"+transformedCode, "insert");
    const {function_body} = ins;    
    assert(function_body.match(/self\._insert\s*\([^(]*\)/));
  }
})

You should pass self.root and key to your _insert() call.

js
({ test: () =>
  {
    const transformedCode = code.replace(/\r/g, "");        
    const ins = __helpers.python.getDef("\n"+transformedCode, "insert");
    const {function_body} = ins;    
    assert(function_body.match(/self\._insert\s*\(\s*self\.root\s*,\s*key\s*\)/));
  }
})

You should assign the return value of your _insert() call to self.root.

js
({ test: () =>
  {
    const transformedCode = code.replace(/\r/g, "");        
    const ins = __helpers.python.getDef("\n"+transformedCode, "insert");
    const {function_body} = ins;    
    assert(function_body.match(/^\s{8}self\.root\s*=\s*self\._insert\s*\(\s*self\.root\s*,\s*key\s*\)/m));
  }
})

--seed--

--seed-contents--

py

class TreeNode:

    def __init__(self, key):
        self.key = key
        self.left = None
        self.right = None


class BinarySearchTree:

    def __init__(self):
        self.root = None

--fcc-editable-region--
    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):
        pass


--fcc-editable-region--