938. Range Sum of BST

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938. Range Sum of BST

Description

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:

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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:

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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 * 10^4].
  • 1 <= Node.val <= 10^5
  • 1 <= low <= high <= 10^5
  • All Node.val are unique .

Hints/Notes

Solution

Language: C++

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
public:
    int rangeSumBST(TreeNode* root, int low, int high) {
        if (!root) {
            return 0;
        }
        int res = 0;

        if (root->val >= low && root->val <= high) {
            res += root->val;
        }

        if (root->val > low) {
            res += rangeSumBST(root->left, low, high);
        }

        if (root->val < high) {
            res += rangeSumBST(root->right, low, high);
        }

        return res;
    }
};