64 lines
1.5 KiB
Haskell
64 lines
1.5 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE RecordWildCards #-}
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module Day02 (Cube(..), Game(..), parse, solveA) where
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import Data.Void (Void)
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import Data.Text (Text)
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import Data.Bifunctor (first)
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import Text.Megaparsec (Parsec, optional, choice, eof, many, sepBy, runParser, errorBundlePretty)
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import Text.Megaparsec.Char (string, space, char, newline)
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import Text.Megaparsec.Char.Lexer (decimal)
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data Cube = R Int | G Int | B Int deriving Show
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data Game = Game
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{ gameId :: Int
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, gameSets :: [[Cube]]
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} deriving Show
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type Parser = Parsec Void Text
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parse :: Text -> Either String [Game]
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parse = first errorBundlePretty . runParser games ""
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where
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cube :: Parser Cube
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cube = do
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_ <- optional space
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number <- decimal
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space
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color <- choice
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[ R <$ string "red"
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, G <$ string "green"
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, B <$ string "blue"
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]
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return . color $ number
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set :: Parser [Cube]
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set = space *> cube `sepBy` char ','
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sets :: Parser [[Cube]]
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sets = set `sepBy` char ';'
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game :: Parser Game
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game = do
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_ <- string "Game"
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space
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gameId <- decimal
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_ <- char ':'
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gameSets <- sets
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_ <- optional newline
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return $ Game {..}
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games :: Parser [Game]
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games = many game <* eof
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solveA :: [Game] -> Int
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solveA = sum . map gameId . filter isValid
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where
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isSetValid :: Cube -> Bool
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isSetValid count = case count of
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R r -> r <= 12
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G g -> g <= 13
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B b -> b <= 14
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isValid :: Game -> Bool
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isValid Game {..} = all (all isSetValid) gameSets
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