# Leetcode: Range Sum of BST

Range Sum of BST

Similar Problems:

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:

1. The number of nodes in the tree is at most 10000.
2. The final answer is guaranteed to be less than 2^31.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

```// Blog link: https://code.dennyzhang.com/range-sum-of-bst
// Basic Idea:
// Complexity: Time O(n), Space O(1)
/**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func rangeSumBST(root *TreeNode, L int, R int) int {
if root == nil { return 0 }
res := 0
if root.Val < L {
res = rangeSumBST(root.Right, L, R)
} else {
if root.Val >= L && root.Val <= R {
res = root.Val + rangeSumBST(root.Left, L, R) + rangeSumBST(root.Right, L, R)
} else {
res = rangeSumBST(root.Left, L, R)
}
}
return res
}
```

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