If your vector is an STL container, the solution is easy:
std::sort(myvec.begin(), myvec.end());
std::erase(std::unique(myvec.begin(), myvec.end()), myvec.end());
According to cppreference (https://en.cppreference.com/w/cpp/algorithm/unique), the elements are shifted around so that the values from myvec.begin() to the return value of std::unique are all unique. The elements after the iterator returned by std::unique are unspecified (useless in every use-case I've seen) so remove them from the std::vector using std::vector::erase.
