Distinct keys in the multimap

From: Przemek (przemyslaw.sliwa_at_gazeta.pl)
Date: 01/31/05 

Date: 31 Jan 2005 05:39:33 -0800

All,

what is the efficient way to find all distinct keys in a multimap.
I use the code

template<class T1, class T2>
set<T1> GetDistinctKeys(multimap<T1, T2> nMap)
{
        T1 temp;
        multimap<T1, T2>::iterator i_ptr;
        set<T1> lSet;

        for(i_ptr=nMap.begin(); i_ptr!=nMap.end(); ++i_ptr)
        {
                lSet.insert(i_ptr->first);
        }

        return lSet;
}

but perhaps you have some fresh ideas :)

Pshem