----- Original Message -----

From: Hicham Mouline

To: boost-users@lists.boost.org

Sent: Monday, February 01, 2010 12:09 PM

Subject: Re: [Boost-users] generate structs with all combinations of members from a given struct

My previous runtime solution was wrong.

I just fixed it now.

#include <iostream>
#include <list>

typedef std::list< std::list<size_t> > main_list_t;

void combinations(main_list_t& m, const size_t* arr, size_t arrsize)
{
if (arrsize==0)
return;

const std::list<size_t> empty_list;
std::list<size_t> l( m.empty()? empty_list: m.back() );
for (size_t s=0; s<arrsize; ++s) {
    l.push_back( arr[s] );
    m.push_back(l);
    l.pop_back();
    combinations(m, arr+s+1, arrsize-s-1);
}
}

int main()
{
const size_t arr[] = { 1, 2, 3, 4, 5 };
const size_t arrsize = sizeof(arr)/sizeof(size_t);

main_list_t mm;
combinations(mm, arr, arrsize);

std::cout<< "size="<< mm.size() <<std::endl;

for (main_list_t::const_iterator i = mm.begin(); i!=mm.end(); ++i) {
    const std::list<size_t>& l = *i;
    for (std::list<size_t>::const_iterator ii = l.begin(); ii!=l.end(); ++ii) {
      std::cout<< *ii << '\t';
    }
    std::cout<<std::endl;
}
}