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