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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.Maybe (catMaybes)
import Data.Void (Void)
import Text.Megaparsec
import Text.Megaparsec.Char
import System.Exit (die)
exampleExpectedOutput = 2
data Passport = Passport { byr :: String
, iyr :: String
, eyr :: String
, hgt :: String
, hcl :: String
, ecl :: String
, pid :: String
} deriving (Show)
type Parser = Parsec Void String
parseString :: String -> Parser String
parseString key = do
void $ string key
void $ char ':'
void (optional $ char '#')
some alphaNumChar
spaces = char ' ' <|> char '\n'
parsePassport :: Parser (Maybe Passport)
parsePassport = do
(byr, iyr, eyr, hgt, hcl, ecl, pid, cid) <- runPermutation $
(,,,,,,,) <$> toPermutationWithDefault Nothing (Just <$> parseString "byr" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "iyr" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "eyr" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "hgt" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "hcl" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "ecl" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "pid" <* spaces)
<*> toPermutationWithDefault Nothing (Just <$> parseString "cid" <* spaces)
void (char '\n')
return $ makePassport byr iyr eyr hgt hcl ecl pid cid
makePassport :: Maybe String -> Maybe String -> Maybe String -> Maybe String -> Maybe String -> Maybe String -> Maybe String -> Maybe String -> Maybe Passport
makePassport (Just byr) ( Just iyr) (Just eyr) (Just hgt) (Just hcl) (Just ecl) (Just pid) _ = Just $ Passport { byr=byr, iyr=iyr, eyr=eyr, hgt=hgt, hcl=hcl, ecl=ecl, pid=pid }
makePassport _ _ _ _ _ _ _ _ = Nothing
parsePassports :: Parser [Passport]
parsePassports = do
passports <- some (parsePassport)
eof
return $ catMaybes passports
parseInput :: String -> IO [Passport]
parseInput filename = do
input <- readFile filename
case runParser parsePassports filename input of
Left bundle -> die $ errorBundlePretty bundle
Right passports -> return passports
compute :: [Passport]-> Int
compute passports = length passports
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
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