for(size_t i = 0; i < v.size() - 1; ++i) {
        std::sort(v.begin()+i, v.end());
        v[i+1] += v[i];
    }

    for(size_t i = 0; i < v.size() - 1; ++i) {
        std::partial_sort(v.begin() + i, v.begin() + i + 2, v.end()); 
        v[i+1] += v[i];
    }