Create 0938-range-sum-of-bst.kt

Author: a93a

kotlin/0938-range-sum-of-bst.kt

@@ -0,0 +1,11 @@
+class Solution {
+    fun rangeSumBST(root: TreeNode?, low: Int, high: Int): Int {
+        root?: return 0
+
+        return if (root.`val` > high) rangeSumBST(root.left, low, high)
+        else if (root.`val` < low) rangeSumBST(root.right, low, high)
+        else root.`val` + 
+            rangeSumBST(root.left, low, high) + 
+            rangeSumBST(root.right, low, high)
+    }
+}