advent05/src/advent05.hs

   1 -- import Debug.Trace
   2
   3 import Numeric
   4 import qualified Data.Set as S
   5
   6 main :: IO ()
   7 main =
   8   do  text <- readFile "data/advent05.txt"
   9       let passes = lines text
  10       print $ part1 passes
  11       print $ part2 passes
  12
  13 part1 = maximum . map convert
  14
  15 part2 passes = S.elemAt 0 $ expecteds `S.difference` knowns
  16   where ns = map convert passes
  17         highest = maximum ns
  18         lowest  = minimum ns
  19         knowns = S.fromList ns
  20         expecteds = S.fromList [lowest..highest]
  21
  22 directionToInt :: Char -> Int
  23 directionToInt dir = if dir `elem` "BR" then 1 else 0
  24
  25 convert :: String -> Int
  26 convert = fst . head . readInt 2 (`elem` "FBLR") directionToInt