938. Range Sum of BST

Posted 2020-11-25 beiyeqingteng

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

 1 class Solution {
 2     public int rangeSumBST(TreeNode root, int L, int R) {
 3        if (root == null) return 0;
 4         if (root.val < L) {
 5             return rangeSumBST(root.right, L, R);
 6         } else if (root.val > R) {
 7             return rangeSumBST(root.left, L, R);
 8         } else {
 9             return root.val + rangeSumBST(root.left, L, root.val) + 
10             rangeSumBST(root.right, root.val, R);
11         }
12     }
13 }