Leetcode) 1315. Sum of Nodes with Even-Valued Grandparent c++

/**
 * 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 sumEvenGrandparent(TreeNode* root) {
        if(root==nullptr) 
		     return 0;
        int sum =0;
        if(root->val%2==0){
            if(root->left!=nullptr && root->left->left!=nullptr)
                sum+=root->left->left->val;
            if(root->left!=nullptr && root->left->right!=nullptr)
                sum+=root->left->right->val;
            if(root->right!=nullptr && root->right->right!=nullptr)
                sum+=root->right->right->val;
            if(root->right!=nullptr && root->right->left!=nullptr)
                sum+=root->right->left->val;
        }
        return sum + sumEvenGrandparent(root->left) + sumEvenGrandparent(root->right);
    }
    
};