938.RangeSumBST.cs

// 938. Range Sum of BST
// Easy

// 4679

// 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].

// 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.

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