75 lines
1.6 KiB
Haskell
75 lines
1.6 KiB
Haskell
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module Day11 where
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import Data.Array
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data Cell = Empty | Occupied | Floor
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deriving (Eq, Show)
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isCell 'L' = True
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isCell '#' = True
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isCell '.' = True
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isCell _ = False
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toCell 'L' = Empty
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toCell '#' = Occupied
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toCell '.' = Floor
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instance Read Cell where
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readsPrec _ (c:rest) = [(toCell c, rest)]
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readList input = [(map toCell cells, rest)]
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where (cells, rest) = span isCell input
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toChar Empty = 'L'
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toChar Occupied = '#'
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toChar Floor = '.'
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type State = Array (Int, Int) Cell
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parse :: String -> State
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parse input = listArray ((1, 1), (width, height)) $ concat lists
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where
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lists :: [[Cell]]
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lists = map read $ lines input
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width = length $ head lists
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height = length lists
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render :: State -> String
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render state = unlines chunks
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where
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(_, (width, _)) = bounds state
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chars = map toChar $ elems state
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chunks = chunk width chars
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chunk n [] = []
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chunk n xs = curr:(chunk n rest)
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where
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(curr, rest) = splitAt n xs
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n (x, y) = (x, y-1)
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s (x, y) = (x, y+1)
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w (x, y) = (x-1, y)
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e (x, y) = (x+1, y)
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ne = n . e
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nw = n . w
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se = s . e
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sw = s . w
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directions x = map ($ x) [n, ne, e, se, s, sw, w, nw]
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(!?) arr ix =
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if inRange (bounds arr) ix
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then Just (arr ! ix)
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else Nothing
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tick :: State -> State
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tick curr = array (bounds curr) $ map nextCell $ assocs curr
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where
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occupiedAdjacent ix =
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length $ filter (== (Just Occupied)) $ map ((!?) curr) $ directions ix
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nextCell c@(ix, Empty)
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| occupiedAdjacent ix == 0 = (ix, Occupied)
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nextCell c@(ix, Occupied)
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| occupiedAdjacent ix >= 4 = (ix, Empty)
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nextCell x = x
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