c++ combination by next_permutation

#include <iostream>
#include <algorithm>
#include <vector>

int main() {
    int n, r;
    n = ;
    r = ;

    std::vector<bool> v(n);
    std::fill(v.end() - r, v.end(), true);
    std::vector< std::vector<int> > sequence_vector;

    do {
        std::vector<int> sequence;
        for (int i = ; i < n; ++i) {
            if (v[i]) {
                std::cout << (i + ) << " ";
                sequence.push_back(i+);
            }
        }
        std::cout << "\n";
        sequence_vector.push_back(sequence);
    } while (std::next_permutation(v.begin(), v.end()));

    std::cout<<"from vector"<<std::endl;

    std::vector<int>::iterator iterator_sequence;
    std::vector< std::vector<int> >::iterator iterator_sequence_vector;
    for(iterator_sequence_vector = sequence_vector.begin();
      iterator_sequence_vector != sequence_vector.end(); iterator_sequence_vector++){
      for (iterator_sequence = (*iterator_sequence_vector).begin();
        iterator_sequence !=  (*iterator_sequence_vector).end(); iterator_sequence++){
        std::cout<<*iterator_sequence<<" ";
      }
      std::cout<<std::endl;
    }

    return ;
}