advent08/src/advent08.hs

   1 import Data.List
   2 import Data.List.Split
   3 import Data.Char
   4 import Data.Ord
   5 import Data.Function
   6
   7 main :: IO ()
   8 main = do
   9         text <- readFile "data/advent08.txt"
  10         let digits = successfulParse text
  11         let layers = chunksOf (imageWidth * imageHeight) digits
  12         print $ part1 layers
  13         putStrLn $ part2 layers
  14
  15
  16 imageWidth = 25
  17 imageHeight = 6
  18
  19 part1 layers = (count 1 target) * (count 2 target)
  20     where target = minimumBy (comparing (count 0)) layers
  21
  22 part2 layers = unlines rows
  23     where pixelLayers = transpose layers
  24           pixels = map firstVisible pixelLayers
  25           dPixels = map showPixel pixels
  26           pixelRows = chunksOf imageWidth dPixels
  27           rows = map concat pixelRows
  28
  29
  30 firstVisible = head . dropWhile (== 2)
  31
  32 showPixel 0 = " "
  33 showPixel 1 = "\x2588"
  34
  35
  36 count n = length . filter (== n)
  37
  38 -- Count the number of times a predicate is true
  39 -- (Taken from GHC API utility functions)
  40
  41 -- count :: (a -> Bool) -> [a] -> Int
  42 -- count p = go 0
  43 --   where go !n [] = n
  44 --         go !n (x:xs) | p x       = go (n+1) xs
  45 --                      | otherwise = go n xs
  46
  47
  48 successfulParse :: String -> [Int]
  49 successfulParse input = map digitToInt input