We're a place where coders share, stay up-to-date and grow their careers.

I used Haskell. Definitely not the most efficient or optimized solution:

module Main where import qualified Data.Map.Strict as M import Data.Maybe (mapMaybe) type Coordinate = (Int, Int) toCoordinateMap :: [[a]] -> M.Map (Int, Int) a toCoordinateMap a = M.fromList $ do (y, row) <- zip [0 ..] a (x, v) <- zip [0 ..] row pure ((x, y), v) findAdjSeats :: Coordinate -> M.Map (Int, Int) Char -> [Coordinate] findAdjSeats (x, y) seats = filter (`M.member` seats) [ (x-1, y-1), (x, y-1), (x+1, y-1), (x-1, y), (x+1, y), (x-1, y+1), (x, y+1), (x+1, y+1) ] findFirstSeatInSight :: Coordinate -> M.Map Coordinate Char -> [Coordinate] findFirstSeatInSight coord seatMap = mapMaybe (firstInSight coord) [ (-1, -1), (0, -1), (1, -1), (-1, 0), (1, 0), (-1, 1), (0, 1), (1, 1) ] where firstInSight (x, y) (dx, dy) = (x-dx, y-dy) `M.lookup` seatMap >>= aux where aux seat = if seat == 'L' || seat == '#' then Just (x-dx, y-dy) else firstInSight (x-dx, y-dy) (dx, dy) runSimulation :: M.Map Coordinate Char -> (Coordinate -> M.Map Coordinate Char -> [Coordinate]) -> Int -> Int runSimulation seatMap findAdjSeatsF occupiedSeats = if seatMap == nextCycle then length $ M.filter (== '#') nextCycle else runSimulation nextCycle findAdjSeatsF occupiedSeats where noOccupiedAdjSeats = not . any ((== Just '#') . (`M.lookup` seatMap)) moreOrEqThanNOccupiedSeats n = (>= n) . length . filter ((== Just '#') . (`M.lookup` seatMap)) nextCycle = M.mapWithKey (\coordinate c -> case c of '.' -> '.' 'L' -> if noOccupiedAdjSeats $ findAdjSeatsF coordinate seatMap then '#' else 'L' '#' -> if moreOrEqThanNOccupiedSeats occupiedSeats $ findAdjSeatsF coordinate seatMap then 'L' else '#' _ -> error $ "cannot do" ++ show c ) seatMap main :: IO () main = do input <- lines <$> readFile "input.txt" let seatMap = toCoordinateMap input print $ runSimulation seatMap findAdjSeats 4 print $ runSimulation seatMap findFirstSeatInSight 5

Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink.

Hide child comments as well

Confirm

For further actions, you may consider blocking this person and/or reporting abuse

I used Haskell. Definitely not the most efficient or optimized solution: