Question

I have a small problem where I need to find all possible paths given a set of numbers. For example, lets say we have numbers 1, 2 and 3. I need to find all the possible combinations. The result for this simple case is:
path_1 = 1
path_2 = 2
path_3 = 3
path_4 = 1, 2
path_5 = 1, 3
path_6 = 2, 3
path_7 = 1, 2, 3

It is simple to see that the number of paths is (2^n)-1, so for 3 elements, it is 7, and so on. It is quite simple to do this by hand for a small number of elements, but as the numbers get big, it gets harder and harder.

Someone has suggested that I can use the boost graph library for this problem, but am not quite sure how to do as I do not have enough experience with it. Any help would be much appreciated.

Thanks in advance

Answer 1

template< class It >
void compute_all_possible_paths( path_collection_t& res, It b, It e ) {
    std::size_t curVecSize = res.size();
    for( std::size_t i = 0; i < curVecSize; i++ ) {
        path_t p;
        p.reserve( res[i].size() + 1 );
        std::copy( res[i].begin(), res[i].end(), std::back_inserter(p) );
        p.push_back( *b );
        res.push_back( p );
    }
    path_t p;
    p.push_back( *b );
    res.push_back( p );
    if( ++b == e ) return ;
    compute_all_possible_paths( res, b, e );
}