How to generate all variations with repetitions of a string?

Question

I want to generate all variations with repetitions of a string in C++ and I\'d highly prefer a non-recursive algorithm. I\'ve come up with a recursive algorithm in the past

Answer 1

STL like function for next_variation. Accept iterators of any container of number like type. You can use float/doubles also. Algorithm it self is very simple. Requirement for iterator is to be only forward. Even a std::list<...> can be used.

template
 bool next_variation
  (
       _Titerator const& _First
     , _Titerator const& _Last
     , _Tnumber const& _Upper
     , _Tnumber const& _Start = 0
     , _Tnumber const& _Step  = 1
  )
  {
   _Titerator _Next = _First;
   while( _Next  != _Last )
    {
      *_Next += _Step;
     if( *_Next < _Upper )
      {
       return true;
      }
     (*_Next) = _Start;
     ++_Next;
    }
   return false;
  }

int main( int argc, char *argv[] )
 {
  std::string s("aaaa");
  do{
      std::cout << s << std::endl;
  }while (next_variation(s.begin(), s.end(), 'c', 'a'));

  std::vector< double > dd(3,1);
  do{
   std::cout << dd[0] << "," << dd[1] << "," << dd[2] << ","  << std::endl;
  }while( next_variation( dd.begin(), dd.end(), 5, 1, 0.5 ) );

  return EXIT_SUCCESS;
 }