1315. Sum of Nodes with Even-Valued Grandparent.cpp

/**
 * 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 sum = 0;
    int sumEvenGrandparent(TreeNode* root) {
        dfs(root,NULL,NULL);
        return sum;
        
    }
    
    void dfs(TreeNode* root,TreeNode* parent,TreeNode* grandparent)
    {
        if(root==NULL) return ;
        
        if(grandparent && grandparent->val % 2==0)
        {
            sum +=root->val;
        }
        dfs(root->left,root,parent);
        dfs(root->right,root,parent);


    }
};