Produce Unique

template<typename Container>
Container produce_unique(Container c){
    Container rtn;
    std::sort(c.begin(), c.end());
    std::unique_copy(c.begin(), c.end(), std::back_inserter(rtn));
    return rtn;
}

template<typename Container, typename T = typename Container::value_type>
Container produce_unique2(const Container& c){
    Container rtn;
    std::unordered_set<T> st;
    std::copy_if(c.begin(), c.end(), std::back_inserter(rtn), [&st](const T& t){ return st.insert(t).second; });
    return rtn;
}