# Range Sum Of BST Problem

## Description

LeetCode Problem 938.

Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high].

Example 1:

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Input: root = [10,5,15,3,7,null,18], low = 7, high = 15
Output: 32
Explanation: Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.
``````

Example 2:

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Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
Output: 23
Explanation: Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.
``````

Constraints:

• The number of nodes in the tree is in the range [1, 2 * 10^4].
• 1 <= Node.val <= 10^5
• 1 <= low <= high <= 10^5
• All Node.val are unique.

## Sample C++ Code

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/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode() : val(0), left(nullptr), right(nullptr) {}
*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
int ans = 0;
int rangeSumBST(TreeNode* root, int L, int R) {
if (root == NULL)
return ans;
if ((root->val >= L) && (root->val <= R))
ans += root->val;
if (root->val > L)
rangeSumBST(root->left, L, R);
if (root->val < R)
rangeSumBST(root->right, L, R);

return ans;

}
};
``````