std::move_iterator was my first thought too, but I'm not sure if it works, since the key type for std::unordered_map is defined to be const, so you may have to

std::move_iterator was my first thought too, but I'm not sure if it works, since the key type for std::unordered_map is defined to be const, so you may have to make a copy anyway. Maybe use a vector-of-pointer-to-pair, since we're leaving the map around and we don't really need the vector to own anything.