Re: Multimap: how to get a key list?

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Rui Maciel writes:


What nested loops? Only one loop is required to iterate over the multimap.

There is no single function that gives you a set of all keys stored in the
multimap, but a single loop is all that's needed to retrieve all the keys.
It's fairly easy to define a template function that gives them to you,
something like this:

template<typename multimap_t>
void keys(const multimap_t &m,
          std::set<typename multimap_t::key_type> &k)
{
    for (typename multimap_t::const_iterator b(m.begin()), e(m.end());
         b != e; ++b)
    {
         k.insert(b->first);
    }
}

The std::set automatically takes care of deduping the multimap's keys.

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