range-sum-of-bst.java

// 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.
//
//
//  
// 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.
//
//


/**
 * 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) {
        if(root == null) return 0;
        if (root.val < L) return rangeSumBST(root.right,L,R);
        if (root.val > R) return rangeSumBST(root.left,L,R);
        return root.val + rangeSumBST(root.left,L,R) +rangeSumBST(root.right,L,R);
    }
}