0938 - Range Sum of BST

0938 - Range Sum of BST

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].

Examples

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.

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.

Constraints

• The number of nodes in the tree is in the range [1, 2 * 104].

• 1 <= Node.val <= 105

• 1 <= low <= high <= 105

• All Node.val are unique.

Java Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    int sum;
    public int rangeSumBST(TreeNode root, int low, int high) {
        sum = 0;
        dfs(root, low, high);
        return sum;
    }
    
    public void dfs(TreeNode node, int low, int high) {
        if(node != null) {
            if(low <= node.val && node.val <= high) sum += node.val;
            if(low < node.val) dfs(node.left, low, high);
            if(node.val < high) dfs(node.right, low, high);
        }
    }
}