938.md

• https://leetcode-cn.com/problems/range-sum-of-bst/

/**
* Definition for a binary tree node. public class TreeNode { int val; TreeNode
* left; TreeNode right; TreeNode(int x) { val = x; } }
*/
    class Solution {
        public int rangeSumBST(TreeNode root, int L, int R) {
            if(root==null){return 0;}
            if(root.val<L){
               return rangeSumBST(root.right, L, R);
            }else if(root.val>R){
                return rangeSumBST(root.left, L, R);
            }else{
                return root.val+rangeSumBST(root.left, L, R)+rangeSumBST(root.right, L, R);
            }
        }
    }