1315. Sum of Nodes with Even-Valued Grandparent

Given the root of a binary tree, return the sum of values of nodes with an even-valued grandparent. If there are no nodes with an even-valued grandparent, return 0.

A grandparent of a node is the parent of its parent if it exists.

/**
 * 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 {
    int helper(TreeNode* node, bool grand, bool parent) {
        if(!node) return 0;
        int res = grand ? node->val : 0;
        res += helper(node->left, parent, !(node->val & 1));
        res += helper(node->right, parent, !(node->val & 1));
        return res;
    }
public:
    int sumEvenGrandparent(TreeNode* root) {
        return helper(root, false, false);
    }
};