Pick up to M from N numbers from a list

main.cpp

#include <iostream>
#include <vector>


using namespace std;
typedef std::vector<uint8_t> choices_t;

void printVec( choices_t& picked ) {
    for (uint8_t num : picked) cout << (int) num << " ";
    cout << "\n";
}

void pickInt( choices_t& picked , uint8_t choice )
{
    picked.push_back(  choice);
}

void popInt( choices_t& picked  )
{
    picked.pop_back();
}


void MfromN( uint8_t m, uint8_t n  , uint8_t n_start , choices_t& picked)
{

    if ( m ==0) {
        printVec(picked);
        return;
    }


    for (int i= n_start  ; i < n ; ++i) {
        pickInt( picked , i );
        MfromN( m - 1, n , i + 1, picked );
        popInt( picked );
    }

}

void uptoMfromN( uint8_t m , uint8_t n )
{
    if (m == 0) return;
    std::vector<uint8_t> picked;
    MfromN( m , n , 0 , picked);
    uptoMfromN( m - 1 , n);
}



int main()
{
    uint8_t res[1];
    std::vector<uint8_t> picked;
    uptoMfromN( 3,6  );

    return 0;
}