34 lines
1.1 KiB
Haskell
34 lines
1.1 KiB
Haskell
module Day24 where
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import AoC
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import Conway
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import Data.List
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import qualified Data.Set as S
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import Optics.Core hiding (Index)
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import Optics.TH
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data Coord = Coord { east :: Int
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, northeast :: Int
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} deriving (Eq, Ord)
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instance Index Coord where
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neighbours c = map (addIndex c . uncurry Coord) offsets
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where offsets = [(0, -1), (0, 1), (1, -1), (1, 0), (-1, 0), (-1, 1)]
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addIndex (Coord x1 y1) (Coord x2 y2) = Coord (x1 + x2) (y1 + y2)
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parseSteps :: String -> Coord
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parseSteps [] = Coord 0 0
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parseSteps xs = case xs of
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('n':'w':xs) -> go (-1, 1) xs
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('w':xs) -> go (-1, 0) xs
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('s':'w':xs) -> go (0, -1) xs
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('n':'e':xs) -> go (0, 1) xs
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('e':xs) -> go (1, 0) xs
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('s':'e':xs) -> go (1, -1) xs
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where go (e, ne) xs = addIndex (Coord e ne) $ parseSteps xs
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main = runAoC (onlySet . map parseSteps . lines) length (length . conwayN 100 . S.fromList)
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where onlySet = map head . filter (odd . length) . group . sort
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conwayN n = last . take n . tail . iterate (update (==2) (`notElem` [1, 2]))
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