1315. Sum of Nodes with Even-Valued Grandparent

#include <iostream>
#include <stack>
#include <queue>
#include "init_tree.hpp"

using namespace std;

struct familyMember {
    TreeNode* currentNode;
    queue<int> ancestors;
};

class Solution {
public:
    int sumEvenGrandparent(TreeNode* root) {
        int sum = 0;
        stack<familyMember> mstack;

        if (root == nullptr)
            return 0;
        else {
            familyMember froot;
            froot.currentNode = root;
            mstack.push(froot);
        }

        while(!mstack.empty()) {
            familyMember current = mstack.top();
            mstack.pop();

            if (current.ancestors.size() == 2) {
                if (current.ancestors.front() % 2 == 0) {
                    sum += current.currentNode->val;
                    // cout << "child = " << current.currentNode->val << endl;
                }
                current.ancestors.pop();
            }

            // insert self as parent for leafs
            queue<int> newAncestors;
            if (!current.ancestors.empty())
                newAncestors.push(current.ancestors.front());
            newAncestors.push(current.currentNode->val);

            if (current.currentNode->left != nullptr) {
                familyMember fleft;
                fleft.ancestors = newAncestors;
                fleft.currentNode = current.currentNode->left;
                mstack.push(fleft);
            }
            if (current.currentNode->right != nullptr) {
                familyMember fright;
                fright.ancestors = newAncestors;
                fright.currentNode = current.currentNode->right;
                mstack.push(fright);
            }
        }

        return sum;
    }
};