LeetCode - 938. Range Sum of BST(Tree, DFS, Binary Tree)

문제

Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high].

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

Example 1:

Input: root = [10,5,15,3,7,null,18], low = 7, high = 15
Output: 32
Explanation: Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
Output: 23
Explanation: Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.

풀이

class Solution {
    
    public int rangeSumBST(TreeNode root, int low, int high) {
        if(root == null) return 0;
        int sum = 0;
        if(root.val >= low && root.val <= high) sum+=root.val;
        
        return sum+rangeSumBST(root.left,low,high)+rangeSumBST(root.right,low,high); 
    }
}