LeetCode #938. Range Sum of BST 二叉搜索树的范围和

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

二叉树中序遍历

二叉搜索树性质：一个节点大于所有其左子树的节点，小于其所有右子树的节点

 /**
  * 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) {
         int result = 0;

         if (root != null) {
             if (root.val >= L && root.val <= R) {
                 result += root.val;
             }
             result += rangeSumBST(root.left, L, R);
             result += rangeSumBST(root.right, L, R);
         }
         return result;
     }
 }