45 lines
1.2 KiB
Haskell
45 lines
1.2 KiB
Haskell
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module Puzzles.Day2 (puzzle2) where
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import Control.Monad
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import Data.Functor
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import Data.Maybe
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import Data.Text (Text)
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import Data.Text qualified as T
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import Puzzle
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import Text.Megaparsec
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import Text.Megaparsec.Char
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import Text.Megaparsec.Char.Lexer qualified as Lex
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puzzle2 :: Puzzle
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puzzle2 =
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Puzzle
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{ number = 2
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, parser = (<* newline) $ flip sepBy (char ',') $ (,) <$> (Lex.decimal <* char '-') <*> Lex.decimal
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, parts =
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[ T.show
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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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, T.show
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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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}
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newtype ID = ID Int
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deriving newtype (Eq, Ord, Show, Num, Enum)
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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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