Range Sum of BST

Author: anantkaushik

938-range-sum-of-bst.py

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+"""
+Problem Link: https://leetcode.com/problems/range-sum-of-bst/
+
+Given the root node of a binary search tree, return the sum of values of all nodes with value 
+between L and R (inclusive).
+The binary search tree is guaranteed to have unique values.
+
+Example 1:
+Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
+Output: 32
+
+Example 2:
+Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
+Output: 23
+ 
+Note:
+The number of nodes in the tree is at most 10000.
+The final answer is guaranteed to be less than 2^31.
+"""
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def rangeSumBST(self, root: TreeNode, L: int, R: int) -> int:
+        def dfs(node):
+            if node:
+                if L<= node.val <= R:
+                    self.ans += node.val
+                if L < node.val:
+                    dfs(node.left)
+                if node.val < R:
+                    dfs(node.right)
+        self.ans = 0
+        dfs(root)
+        return self.ans