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