Python 3 (300ms) | Simple DFS | Easy to Understand
\nclass Solution:\n    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:\n        if root is None:\n            return 0\n        s=0
```\nclass Solution:\n    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:\n        if root is None:\n            return 0\n        s=0\n        if root.val>=low and root.val<=high:\n            s=s+root.val\n        s=s+self.rangeSumBST(root.left,low,high)\n        s=s+self.rangeSumBST(root.right,low,high)\n        return s\n```
['Depth-First Search', 'Recursion', 'Binary Tree', 'Python', 'Python3']