Submission #764522

---

Source Code Expand

import qualified Data.Map.Lazy as M

main :: IO ()
main = do
  [h,w] <- fmap read . words <$> getLine
  s <- concat . lines <$> getContents
  let m = M.fromList $ zip [(x,y)| x <- [1..w], y <- [1..h]] s
  let m' = calc ('.','#') m
  if m == calc ('#','.') m' then
    putStrLn "possible" >> (putStrLn . unlines . toList' w $ M.elems m')
  else
    putStrLn "impossible"


calc :: (Char, Char) -> M.Map (Int,Int) Char -> M.Map (Int, Int) Char
calc (w,b) m = M.mapWithKey calc' m
  where
    calc' k _ = change . all (maybe True (== b) . flip M.lookup m) $ around k
    change t = if t then b else w
    around (x,y) = [(x',y')| x' <- [x-1,x,x+1], y' <- [y-1,y,y+1]]

toList' :: Int -> String -> [String]
toList' w = loop
  where
    loop [] = []
    loop xs = (\(a,b) -> a : loop b) $ splitAt w xs

Submission Info

Judge Result