66 lines
2.4 KiB
Haskell
66 lines
2.4 KiB
Haskell
-- requires cabal install --lib megaparsec parser-combinators
|
|
module Main (main) where
|
|
import Control.Monad (void, when)
|
|
import Data.List qualified as L
|
|
import Data.Map qualified as M
|
|
import Data.Maybe (catMaybes)
|
|
import Data.Set qualified as S
|
|
import Data.Void (Void)
|
|
import Text.Megaparsec
|
|
import Text.Megaparsec.Char
|
|
import System.Exit (die)
|
|
|
|
exampleExpectedOutput = 5
|
|
|
|
newtype Ingredient = Ingredient String deriving (Eq, Ord, Read, Show)
|
|
newtype Allergen = Allergen String deriving (Eq, Ord, Read, Show)
|
|
type Rule = ([Ingredient], [Allergen])
|
|
type Input = [Rule]
|
|
|
|
type Parser = Parsec Void String
|
|
|
|
parseRule :: Parser Rule
|
|
parseRule = do
|
|
ingredients <- some ((Ingredient <$> some letterChar) <* char ' ')
|
|
void $ string "(contains "
|
|
allergens <- some ((Allergen <$> some letterChar) <* optional (string ", "))
|
|
void $ string ")\n"
|
|
return $ (ingredients, allergens)
|
|
|
|
parseInput' :: Parser Input
|
|
parseInput' = some parseRule <* eof
|
|
|
|
parseInput :: String -> IO Input
|
|
parseInput filename = do
|
|
input <- readFile filename
|
|
case runParser parseInput' filename input of
|
|
Left bundle -> die $ errorBundlePretty bundle
|
|
Right input' -> return input'
|
|
|
|
compute :: Input -> Int
|
|
compute rules = sum . map count $ filter isUnused ingredients
|
|
where
|
|
ingredients :: [Ingredient]
|
|
ingredients = S.elems . S.fromList . concat $ map fst rules
|
|
candidates :: [[Ingredient]]
|
|
candidates = M.elems candidatesMap
|
|
candidatesMap :: M.Map Allergen [Ingredient]
|
|
candidatesMap = L.foldl' appendIngredientsForRule M.empty rules
|
|
appendIngredientsForRule :: M.Map Allergen [Ingredient] -> Rule -> M.Map Allergen [Ingredient]
|
|
appendIngredientsForRule m (is, as) = L.foldl' (appendIngredientsForAllergen is) m as
|
|
appendIngredientsForAllergen :: [Ingredient] -> M.Map Allergen [Ingredient] -> Allergen -> M.Map Allergen [Ingredient]
|
|
appendIngredientsForAllergen is m a = case M.lookup a m of
|
|
Nothing -> M.insert a is m
|
|
Just is' -> M.insert a (L.intersect is is') m
|
|
isUnused :: Ingredient -> Bool
|
|
isUnused i = (catMaybes $ map (L.elemIndex i) candidates) == []
|
|
count :: Ingredient -> Int
|
|
count i = sum $ map (length . L.elemIndices i) (map fst rules)
|
|
|
|
main :: IO ()
|
|
main = do
|
|
example <- parseInput "example"
|
|
let exampleOutput = compute example
|
|
when (exampleOutput /= exampleExpectedOutput) (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
|
|
input <- parseInput "input"
|
|
print $ compute input
|