Question

I have a multimap and I would like to get a set of sets – which would group together all the items of type A in the multimap that share the same key. Is there a built-in way to do this in STL?

Answer 1

I don’t think there is a built-in way. However it is easy to do manually:

std::multimap<key, value> mm;
// ...
std::multimap<key, value>::const_iterator i = mm.begin();
while (i != mm.end())
{
    std::multimap<key, value>::const_iterator end = mm.upper_bound(i->first);
    // construct a set from the values in [i, end)
    i = end;
}

Or something like that.