78 lines
2.1 KiB
Haskell
78 lines
2.1 KiB
Haskell
|
-- requires cabal install --lib megaparsec parser-combinators
|
||
|
module Main (main) where
|
||
|
import Control.Monad (void, when)
|
||
|
import qualified Data.Set as S
|
||
|
import Data.Void (Void)
|
||
|
import Text.Megaparsec
|
||
|
import Text.Megaparsec.Char
|
||
|
import System.Exit (die)
|
||
|
|
||
|
exampleExpectedOutput = 4
|
||
|
|
||
|
data Bag = Bag { name :: String
|
||
|
, contents :: [(Int, String)]
|
||
|
} deriving (Show)
|
||
|
|
||
|
type Parser = Parsec Void String
|
||
|
|
||
|
parseName :: Parser String
|
||
|
parseName = do
|
||
|
adjective <- some letterChar
|
||
|
void (char ' ')
|
||
|
color <- some letterChar
|
||
|
return $ adjective ++ " " ++ color
|
||
|
|
||
|
parseInt :: Parser Int
|
||
|
parseInt = do
|
||
|
i <- some digitChar
|
||
|
return $ read i
|
||
|
|
||
|
parseContent :: Parser (Int, String)
|
||
|
parseContent = do
|
||
|
i <- parseInt
|
||
|
void (char ' ')
|
||
|
name <- parseName
|
||
|
void (string " bag")
|
||
|
void (optional $ char 's')
|
||
|
void (string ", " <|> string ".")
|
||
|
return (i, name)
|
||
|
|
||
|
parseContents :: Parser [(Int, String)]
|
||
|
parseContents = some parseContent <|> (string "no other bags." *> return [])
|
||
|
|
||
|
parseBag :: Parser Bag
|
||
|
parseBag = do
|
||
|
name <- parseName
|
||
|
void $ string " bags contain "
|
||
|
contents <- parseContents
|
||
|
void (char '\n')
|
||
|
return $ Bag { name=name, contents=contents }
|
||
|
|
||
|
parseBags :: Parser [Bag]
|
||
|
parseBags = some parseBag <* eof
|
||
|
|
||
|
parseInput :: String -> IO [Bag]
|
||
|
parseInput filename = do
|
||
|
input <- readFile filename
|
||
|
case runParser parseBags filename input of
|
||
|
Left bundle -> die $ errorBundlePretty bundle
|
||
|
Right bags -> return bags
|
||
|
|
||
|
compute :: [Bag]-> Int
|
||
|
compute bags = (length . compute' $ S.fromList ["shiny gold"]) - 1
|
||
|
where
|
||
|
bagsContaining :: S.Set String -> S.Set String
|
||
|
bagsContaining s = S.union s $ S.fromList . (map name) $ filter (\x -> not . S.null . S.intersection s $ S.fromList . (map snd) . contents $ x) bags
|
||
|
compute' :: S.Set String -> S.Set String
|
||
|
compute' s = if s == s' then s else compute' s'
|
||
|
where
|
||
|
s' = bagsContaining s
|
||
|
|
||
|
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
|