CrossingSet reverse_tb(CrossingSet const &cr, unsigned split, std::vector<double> max) {
    CrossingSet ret;
    for(unsigned i = 0; i < cr.size(); i++) {
        Crossings res = reverse_tb(cr[i], split, max);
        if(i >= split) std::reverse(res.begin(), res.end());
        ret.push_back(res);
    }
    return ret;
}