Same. I just wrote it in the order I thought it out though -- put the difficult part on the left, then filled in the simple part on the right. Would have changed it if I looked at it for more than a few seconds before submitting.

Honestly, I think it has to do with reading comprehension. I submitted this solution as well, yet for some reason I find the other one easier to read at a glance.

"set() method is used to convert any of the iterable to sequence of iterable elements with distinct elements, commonly called Set."
Meaning, a set is the same basic group of characters as the original, except it excludes duplicates and it is not in order.