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module Main where
import Control.Monad
import Data.Map (Map)
import qualified Data.Map as M
import Data.Maybe
import Utils
type Pos = (Int, Int, Int, Int)
toBool '#' = True
toBool '.' = False
gridMap :: String -> Map Pos Bool
gridMap s = M.fromList
[((x,y,0,0), toBool a)
| (y, row) <- zip [0..] rows
, (x, a) <- zip [0..] row
]
where rows = lines s
around :: Pos -> [Pos]
around (x,y,z,w) =
[(x+x', y+y', z+z', w+w')
| x' <- [-1..1]
, y' <- [-1..1]
, z' <- [-1..1]
, w' <- [-1..1]
, (x',y',z',w') /= (0,0,0,0)
]
convert True 2 = True
convert True 3 = True
convert False 3 = True
convert _ _ = False
doStep :: Map Pos Bool -> Map Pos Bool
doStep m = M.mapWithKey fn $ m <> M.fromList [(p, False) | p <- concatMap around (M.keys m)]
where fn pos v = convert v n
where n = howMany id $ map (fromMaybe False . flip M.lookup m) $ around pos
main :: IO ()
main = do
n <- readFile "input/17"
let grid = gridMap n
print $ M.size $ M.filter id (iterate doStep grid !! 6)
|
