src/advent14/advent14.hs

   1 import Data.List.Split (chunksOf)
   2 import Data.Char (ord)
   3 import Text.Printf (printf)
   4 import Data.Bits (xor)
   5 import qualified Data.Map.Strict as M
   6 import Data.Map.Strict ((!))
   7 import qualified Data.Graph as G
   8
   9 type CellMap = M.Map (Int, Int) Bool
  10
  11 puzzleKey = "xlqgujun"
  12
  13 main :: IO ()
  14 main = do
  15   print $ part1 puzzleKey
  16
  17 -- part1 :: String -> Int
  18 -- part1 key = sum rowCounts
  19 --     where hashes = map knotHash $ rowSpecs key
  20 --           rowCounts = map (countSetBits . binify) hashes
  21
  22 part1 :: String -> Int
  23 part1 key = sum rowCounts
  24     where binHashes = map binHash $ rowSpecs key
  25           rowCounts = map countSetBits binHashes
  26
  27
  28 -- part2 :: String -> Int
  29 part2 key = cells
  30     where binHashes = map binHash $ rowSpecs key
  31           cells = presentCells binHashes
  32
  33 binHash :: String -> String
  34 binHash = binify . knotHash
  35
  36 numKey :: (Int, Int) -> Int
  37 numKey (r, c) = 128 * r + c
  38
  39
  40 presentCells :: [String] -> CellMap
  41 presentCells binHashes = M.fromList [((r, c), True) | r <- [0..127], c <- [0..127], (binHashes!!r)!!c == '1']
  42
  43 adjacentCells :: CellMap -> (Int, Int) -> [(Int, Int)]
  44 adjacentCells cells (r, c) = filter (\k -> M.member k cells) possibles
  45   where possibles = [(r, c - 1), (r, c + 1), (r - 1, c), (r + 1, c)]
  46         -- isPresent rc = length $ rc `member` cells
  47
  48
  49 cellEdges :: CellMap -> Int
  50 cellEdges cells = length $ G.stronglyConnComp [(k, numKey k, map numKey $ adjacentCells cells k) | k <- M.keys cells]
  51
  52 rowSpecs :: String -> [String]
  53 rowSpecs key = map (((key ++ "-") ++) . show) [0..127]
  54
  55 countSetBits :: String -> Int
  56 countSetBits = length . filter (== '1')
  57
  58
  59
  60 knotHash :: String -> [Int]
  61 knotHash input = densify tied
  62     where (tied, _, _) = foldl step ([0..255], 0, 0) hashTerms
  63           hashTerms = mkHashTerms input
  64
  65 step :: ([Int], Int, Int) -> Int -> ([Int], Int, Int)
  66 step (original, start, skip) len = (replaced, start', skip + 1)
  67     where replaced = tie original start len
  68           start' = (start + len + skip) `mod` (length original)
  69
  70 tie :: [a] -> Int -> Int -> [a]
  71 tie original start len = replace original replacement start
  72     where replacement = reverse $ extract original start len
  73
  74 extract :: [a] -> Int -> Int -> [a]
  75 extract items from len = take len $ drop from $ items ++ items
  76
  77 replace :: [a] -> [a] -> Int -> [a]
  78 replace original replacement from = take (length original) (start ++ replacement ++ remainder)
  79     where excess = drop (length original - from) replacement
  80           stub = drop (length excess) original
  81           start = take from (excess ++ stub)
  82           remainder = drop (length $ start ++ replacement) original
  83
  84
  85 mkHashTerms :: String -> [Int]
  86 mkHashTerms text = take (length chunk * 64) $ cycle chunk
  87     where chunk = map ord text ++ [17, 31, 73, 47, 23]
  88
  89 hexify :: [Int] -> String
  90 hexify = concatMap (printf "%02x")
  91
  92 binify :: [Int] -> String
  93 binify = concatMap (printf "%08b")
  94
  95 densify :: [Int] -> [Int]
  96 densify ns = codes
  97     where chunks = chunksOf 16 ns
  98           compress = foldl1 xor
  99           codes = map compress chunks