Since the triplets are random you can get inaccurate results only parsing over the triplets once. Puayny is correct in their comment "This solution is incomplete though elegant, it will fail for some test cases currently not included. The 'for l in triplets' loop shouldn't run just once, it should run until there are no more swaps.". Their comment is the most efficient solution however since these are triples you could also just run the loop twice which I think is more than enough to get the correct sequence.