While most answers have concentrated on the ambiguity of preserving order or not - which you never clarified - there is another aspect to consider about uniqueness.

Are nick-john-helena and john-helena-nick really considered two different solutions?

If not, you'll need to sort the result set.

Goes without saying that solutions preserving order are overkill in that case.

FWIW: afaik, my hash solution should always return the keys in the same randomized order , hence sorting wouldn't be strictly necessary. At least within the limits of the same process.

But personally I'd rather play safe and sort.