40 lines
1.1 KiB
Haskell
40 lines
1.1 KiB
Haskell
module Puzzles.Day2 (puzzle) where
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import Pre
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import Data.Text qualified as T
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puzzle :: Puzzle
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puzzle =
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Puzzle
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{ number = 2
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, parser = const $ (<* newline) $ ((,) <$> (decimal <* char '-') <*> decimal) `sepBy` (char ',')
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, parts =
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( sum
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. concatMap
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(mapMaybe (\n -> guard (isRepetition2 n) $> n) . uncurry enumFromTo)
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)
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/\ ( sum
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. concatMap
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(mapMaybe (\n -> guard (isRepetitionN n) $> n) . uncurry enumFromTo)
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)
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/\ nil
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, extraTests = mempty
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}
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newtype ID = ID Int
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deriving newtype (Eq, Ord, Show, Num, Enum, NFData)
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isRepetition2 :: ID -> Bool
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isRepetition2 (T.show -> n) = case T.length n `divMod` 2 of
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(d, 0) -> equalChunks n d
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_ -> False
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isRepetitionN :: ID -> Bool
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isRepetitionN (T.show -> n) = flip any [1 .. T.length n `div` 2] $ equalChunks n
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equalChunks :: Text -> Int -> Bool
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equalChunks n i = case T.chunksOf i n of
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[] -> True
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x : xs -> all (== x) xs
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