Re: Multimap: how to get a key list?

Sam <>
Sun, 28 Feb 2010 17:09:18 -0600
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Rui Maciel writes:

Is there any way to get a list of keys from a multimap besides relying on a couple of nested
loops to assemble that list?

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)

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