best_quadrant_2.cpp

int best_quadrant(Matrix const& m)
{   
    int n = m.size() / 2;
    return accumulate(range(0, n), 0, [&](int sum, int i){
        return accumulate(range(0, n), sum, [&](int sum, int j){
            auto flips = symetric_values(m, n, {i, j});
            return sum + *std::max_element(flips.begin(), flips.end());
        });
    });
}