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 qualified Data.Set as S
   7 import qualified Data.Graph as G
   8 import Control.Parallel.Strategies (parMap, rpar)
   9
  10
  11 type CellSet = S.Set (Int, Int)
  12
  13 puzzleKey = "xlqgujun"
  14
  15 main :: IO ()
  16 main = do
  17   print $ part1 puzzleKey
  18   print $ part2 puzzleKey
  19
  20
  21 part1 :: String -> Int
  22 part1 key = sum rowCounts
  23     where rowCounts = parMap rpar countSetBits $ binHashes key
  24
  25
  26 part2 :: String -> Int
  27 part2 key = length $ cellEdges cells
  28     where cells = presentCells $ binHashes key
  29
  30 binHashes :: String -> [String]
  31 binHashes key = parMap rpar binHash $ rowSpecs key
  32
  33
  34 binHash :: String -> String
  35 binHash = binify . knotHash
  36
  37 numKey :: (Int, Int) -> Int
  38 numKey (r, c) = 128 * r + c
  39
  40
  41 presentCells :: [String] -> CellSet
  42 presentCells bhs = S.fromList [(r, c) | r <- [0..127], c <- [0..127], (bhs!!r)!!c == '1']
  43
  44 adjacentCells :: CellSet -> (Int, Int) -> [(Int, Int)]
  45 adjacentCells cells (r, c) = filter (\k -> S.member k cells) possibles
  46   where possibles = [(r, c - 1), (r, c + 1), (r - 1, c), (r + 1, c)]
  47
  48
  49 cellEdges :: CellSet -> [G.SCC (Int, Int)]
  50 cellEdges cells = G.stronglyConnComp [(k, numKey k, map numKey $ adjacentCells cells k) | k <- S.elems cells]
  51
  52 rowSpecs :: String -> [String]
  53 rowSpecs key = map (((key ++ "-") ++) . show) ([0..127] :: [Integer])
  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