Python Elegant & Short | Recursive | Three lines
\n    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:\n        if root is None:\n            return 0\n        return self.rangeSum
\n    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:\n        if root is None:\n            return 0\n        return self.rangeSumBST(root.left, low, high) + \\\n               self.rangeSumBST(root.right, low, high) + \\\n               root.val * (low <= root.val <= high)\n
['Recursion', 'Python', 'Python3']