利用 set_symmetric_difference 求两个 vector 中不同的所有元素

set<int> VecToSet (const vector<int> &vec)
{
    set<int> tmp_set (vec.cbegin (), vec.cend ());
    return move (tmp_set);
}

void EraseSameNum (set<int> &short_set
                   , set<int> &long_set)
{
    for (auto it = short_set.begin ();
         it != short_set.end ();) {
        auto loc = long_set.find (*it);
        if (loc != long_set.end ()) {
            auto loc2 = it;
            ++it;
            short_set.erase (loc2);
            long_set.erase (loc);
        }
        ++it;
    }
}
set<int> GetDiffNums (const vector<int> &lhs_vec
                        , const vector<int> &rhs_vec)
{
    set<int> lhs_set = VecToSet(lhs_vec);
    set<int> rhs_set = VecToSet(rhs_vec);
    if (lhs_set.size () > rhs_set.size ()) {
        EraseSameNum (rhs_set, lhs_set);
    }
    EraseSameNum (rhs_set, lhs_set);
    set<int> diff_set (lhs_set);
    diff_set.insert (rhs_set.begin(), rhs_set.end());
    return move (diff_set);
}

int main()
{
    using int_v = vector<int>;
    int_v v1{1, 2, 4, 6};
    int_v v2{2, 5, 6, 8, 4};
    set<int> iset = GetDiffNums(v1, v2);  
}

int main ()
{
    using int_v = vector<int>;
    int_v vec1{1, 3, 6};
    int_v vec2{2, 3, 8, 3, 7, 6};
    sort (vec1.begin(), vec1.end());
    sort (vec2.begin(), vec2.end());
    set<int> iset;
    set_symmetric_difference (vec1.begin()
                              , vec1.end()
                              , vec2.begin()
                              , vec2.end()
                              , inserter(
                                iset, iset.begin()));
    return 0;
}