src/advent01/advent01.hs

   1 {-# LANGUAGE NegativeLiterals #-}
   2 {-# LANGUAGE OverloadedStrings #-}
   3
   4 import Data.Text (Text)
   5 import qualified Data.Text.IO as TIO
   6
   7 import Data.Void (Void)
   8
   9 import Text.Megaparsec
  10 import Text.Megaparsec.Char
  11 import qualified Text.Megaparsec.Char.Lexer as L
  12 import qualified Control.Applicative as CA
  13
  14 import Data.IntSet (IntSet)
  15 import qualified Data.IntSet as IntSet
  16
  17 main :: IO ()
  18 main = do
  19         text <- TIO.readFile "data/advent01.txt"
  20         let changes = successfulParse text
  21         print $ part1 changes
  22         print $ part2 changes
  23
  24
  25 part1 :: [Int] -> Int
  26 part1 = sum
  27
  28 part2 :: [Int] -> Int
  29 part2 changes = snd $ head $ dropWhile unRepeated $ scanl merge (IntSet.empty, 0) $ cycle changes
  30
  31
  32 merge :: (IntSet, Int) -> Int -> (IntSet, Int)
  33 merge (s, f) c = (IntSet.insert f s, f+c)
  34
  35 unRepeated :: (IntSet, Int) -> Bool
  36 unRepeated (s, f) = f `IntSet.notMember` s
  37
  38 -- Parse the input file
  39 type Parser = Parsec Void Text
  40
  41 sc :: Parser ()
  42 -- sc = L.space (skipSome spaceChar) CA.empty CA.empty
  43 sc = L.space (skipSome (char ' ')) CA.empty CA.empty
  44
  45
  46 lexeme  = L.lexeme sc
  47 integer = lexeme L.decimal
  48 signedInteger = L.signed sc integer
  49
  50 -- symb = L.symbol sc
  51 -- comma = symb ","
  52
  53
  54 changesP = signedInteger `sepEndBy` newline
  55
  56
  57 successfulParse :: Text -> [Int]
  58 successfulParse input =
  59         case parse changesP "input" input of
  60                 Left  _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
  61                 Right changes -> changes