Discussion on: Advent of Code 2020 Solution Megathread - Day 6: Custom Customs

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OK, today seemed pretty straightforward, although it took me to reach task 2 to have the insight that it was union and then intersect... oh well it is a Sunday :-)

Anyway Haskell was a nice fit and simply used set operations on lists to keep with my somewhat weak goal of using lists.

main  = do xs <- IOT.readFile "day6_input" <&> fmap (map unpack . T.lines) . T.splitOn "\n\n"
           print (sum $ fmap (length . foldr1 union) xs)
           print (sum $ fmap (length . foldr1 intersect) xs)