66 lines
2 KiB
Haskell
66 lines
2 KiB
Haskell
-- requires cabal install --lib megaparsec parser-combinators
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module Main (main) where
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import Control.Applicative.Permutations
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import Control.Monad (void, when)
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import Data.Char qualified as C
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import Data.List qualified as L
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import Data.Map qualified as M
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import Data.Maybe
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import Data.Set qualified as S
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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exampleExpectedOutput = 2286
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data Draw = Draw Int Int Int deriving (Eq, Show)
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data Game = Game Int [Draw] deriving Show
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type Input = [Game]
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type Parser = Parsec Void String
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parseColor :: String -> Parser Int
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parseColor color = read <$> try (some digitChar <* char ' ' <* string color <* optional (string ", "))
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parseDraw :: Parser Draw
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parseDraw = do
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(blue, green, red) <- runPermutation $
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(,,) <$> toPermutationWithDefault 0 (parseColor "blue")
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<*> toPermutationWithDefault 0 (parseColor "green")
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<*> toPermutationWithDefault 0 (parseColor "red")
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void . optional $ string "; "
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return $ Draw blue green red
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parseGame :: Parser Game
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parseGame = do
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id <- read <$> (string "Game " *> some digitChar <* optional (string ": "))
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Game id <$> someTill parseDraw eol
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parseInput' :: Parser Input
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parseInput' = some parseGame <* eof
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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power :: [Int] -> Draw -> [Int]
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power [b, g, r] (Draw b' g' r') = [max b b', max g g', max r r']
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process :: Int -> Game -> Int
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process acc (Game id draws) = acc + product (L.foldl' power [0, 0, 0] draws)
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compute :: Input -> Int
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compute = L.foldl' process 0
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main :: IO ()
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main = do
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example <- parseInput "example"
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let exampleOutput = compute example
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when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
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input <- parseInput "input"
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print $ compute input
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