975. Range Sum of BST

• Difficulty: Easy

• Topics: Tree, Recursion

• Similar Questions:

Problem:

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

Note:

1. The number of nodes in the tree is at most 10000.
2. The final answer is guaranteed to be less than 2^31.

Solutions:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int rangeSumBST(TreeNode* root, int L, int R) {
        if (root == nullptr)    return 0;
        int sum = (root->val >= L && root->val <= R ? root->val : 0);
        if (root->val >= L) {
            sum += rangeSumBST(root->left, L, R);
        }

        if (root->val <= R) {
            sum += rangeSumBST(root->right, L, R);
        }

        return sum;
    }
};