Leetcode 938 Range Sum of BST.go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */


func rangeSumBST(root *TreeNode, low int, high int) int {
    if root == nil {
        return 0
    }
    if root.Val >= low && root.Val <= high {
        return root.Val + rangeSumBST(root.Left,low,high) + rangeSumBST(root.Right,low,high)
    } else if root.Val < low {
        return rangeSumBST(root.Right,low,high)
    } else {
        return rangeSumBST(root.Left,low,high)
    }
    return 0
}