void removeEdge(const city c1, const city c2)
    {
        std::cout << "에지 삭제: " << c1 << "-" << c2 << std::endl;

        auto n1 = static_cast<int>(c1);
        auto n2 = static_cast<int>(c2);
        std::remove_if(data[n1].begin(), data[n1].end(), [n2](const auto& pair) {
            return pair.first == n2;
            });
        std::remove_if(data[n2].begin(), data[n2].end(), [n1](const auto& pair) {
            return pair.first == n1;
            });
    }
};