How to make elements of vector unique? (remove non adjacent duplicates)

Question

I have a vector containing few non-adjacent duplicates.

As a simple example, consider:

2 1 6 1 4 6 2 1 1

I am trying to make this

Answer 1

Without using a temporary set it's possible to do this with (possibly) some loss of performance:

template
Iterator Unique(Iterator first, Iterator last)
{
    while (first != last)
    {
        Iterator next(first);
        last = std::remove(++next, last, *first);
        first = next;
    }

    return last;
}

used as in:

vec.erase( Unique( vec.begin(), vec.end() ), vec.end() );

For smaller data sets, the implementation simplicity and lack of extra allocation required may offset the theoretical higher complexity of using an additional set. Measurement with a representative input is the only way to be sure, though.