adventofcode1615/app/advent15l.hs

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