Create Range_Sum_of_BST.py

Author: WenjingXue

leetcode/Range_Sum_of_BST.py

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+###### The main part is to understand the characteristics of Binary Search Tree,right >= node >= left
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
+        if not root: return 0
+        if root.val > high: return self.rangeSumBST(root.left, low, high)
+        if root.val < low: return self.rangeSumBST(root.right,low,high)
+        return root.val + self.rangeSumBST(root.left, low, high) + self.rangeSumBST(root.right,low,high)
+