advent16i.hs

   1 input = "11100010111110100"
   2 disk1length = 272
   3 disk2length = 35651584
   4
   5 -- input = "10000"
   6 -- disk1length = 20
   7
   8 main :: IO ()
   9 main = do
  10     part1
  11     part2
  12
  13 part1 :: IO ()
  14 part1 = print $ fill disk1length input
  15
  16 part2 :: IO ()
  17 part2 = print $ fill disk2length input
  18
  19 fill :: Int -> String -> String
  20 fill len filler = deBool $ checksum $ take len $ expand len $ enBool filler
  21
  22 enBool :: String -> [Bool]
  23 enBool = map (== '1')
  24
  25 deBool :: [Bool] -> String
  26 deBool = map (\b -> if b then '1' else '0')
  27
  28
  29 expand :: Int -> [Bool] -> [Bool]
  30 expand len = head . dropWhile ((<= len) . length) . iterate expandStep
  31
  32 expandStep :: [Bool] -> [Bool]
  33 expandStep a = a ++ [False] ++ b
  34         where b = map (not) $ reverse a
  35
  36 checksum :: [Bool] -> [Bool]
  37 checksum = head . dropWhile (even . length) . iterate checksumStep
  38
  39 checksumStep :: [Bool] -> [Bool]
  40 checksumStep [] = []
  41 checksumStep [x] = [x]
  42 checksumStep (x:y:xs) = (x==y):(checksumStep xs)
  43