adventofcode1615/app/advent15.hs

   1 module Main(main) where
   2
   3 import Text.Parsec
   4 import Text.ParserCombinators.Parsec.Number
   5
   6 type Disk = (Int -> Bool)
   7
   8 main :: IO ()
   9 main = do
  10     text <- readFile "data/advent15.txt"
  11     let disks = successfulParse $ parseIfile text
  12     part1 disks
  13     part2 disks
  14
  15 part1 :: [Disk] -> IO ()
  16 part1 disks = print $ head $ filter (canFall disks) [0..]
  17
  18 part2 :: [Disk] -> IO ()
  19 part2 disks = print $ head $ filter (canFall disks2) [0..]
  20     where disks2 = disks ++ [diskify 7 11 0]
  21
  22 canFall :: [Disk] -> Int -> Bool
  23 canFall ds i = all (\d -> (d i)) ds
  24
  25
  26 instructionFile = instructionLine `endBy` newline
  27 instructionLine = diskify <$> (string "Disc #" *> int)
  28                           <*> (string " has " *> int)
  29                           <*> (string " positions; at time=0, it is at position " *> int)
  30                           <*  (string ".")
  31
  32 diskify :: Int -> Int -> Int -> (Int -> Bool)
  33 diskify n size pos0 = (\i -> (size + n + pos0 + i) `mod` size == 0)
  34
  35 parseIfile :: String -> Either ParseError [Disk]
  36 parseIfile input = parse instructionFile "(unknown)" input
  37
  38 parseIline :: String -> Either ParseError Disk
  39 parseIline input = parse instructionLine "(unknown)" input
  40
  41 successfulParse :: Either ParseError [a] -> [a]
  42 successfulParse (Left _) = []
  43 successfulParse (Right a) = a