stl::multimap – how do i get groups of data?

by 
pair<Iter, Iter> range = my_multimap.equal_range("Group1");
int total = accumulate(range.first, range.second, 0);

Is one way.

Edit:

If you don’t know the group you are looking for, and are just going through each group, getting the next group’s range can be done like so:

template <typename Pair>
struct Less : public std::binary_function<Pair, Pair, bool>
{
    bool operator()(const Pair &x, const Pair &y) const
    {
        return x.first < y.first;
    }
};

Iter first = mmap.begin();
Iter last = adjacent_find(first, mmap.end(), Less<MultimapType::value_type>());

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