std::flat_multiset<Key,Compare,KeyContainer>::insert_range

Inserts a copy of each element in the range rg into underlying container c as if by:

for (const auto& e : rg)
    c.insert(c.end(), e);

Then, sorts the range of newly inserted elements with respect to compare. Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range.

Each iterator in the range rg is dereferenced exactly once.

If any of the following conditions is satisfied, the behavior is undefined:

• value_type is not EmplaceConstructible into flat_multiset from *ranges::begin(rg)
• rg and *this overlap.

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