40 lines
1.5 KiB
Haskell
40 lines
1.5 KiB
Haskell
{-# LANGUAGE TypeSynonymInstances, FlexibleInstances, DataKinds #-}
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module Day17 where
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import AoC
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import Data.List
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import Data.Vector.Sized (Vector)
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import qualified Data.Vector.Sized as V
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import Data.Map (Map)
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import qualified Data.Map as M
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import Data.Set (Set)
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import qualified Data.Set as S
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class Index i where
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neighbours :: i -> [i]
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addIndex :: i -> i -> i
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instance (Num a, Eq a) => Index (Vector n a) where
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neighbours i = filter (/= i) . V.mapM (flip map [-1, 0, 1] . (+)) $ i
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addIndex = V.zipWith (+)
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counts :: Ord a => [a] -> Map a Int
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counts = M.fromList . map (\xs -> (head xs, length xs)) . group . sort
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neighbourCounts :: (Index i, Ord i) => Set i -> Map i Int
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neighbourCounts = counts . concatMap neighbours . S.elems
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update :: (Index i, Ord i) => (Int -> Bool) -> (Int -> Bool) -> Set i -> Set i
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update create destroy old = M.keysSet $ M.filterWithKey shouldLive $ M.fromSet (flip (M.findWithDefault 0) nCounts) indices
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where nCounts = neighbourCounts old
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indices = S.union old $ M.keysSet nCounts
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shouldLive ix n = if S.notMember ix old then create n else not $ destroy n
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run6 :: (Index i, Ord i) => Set i -> Int
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run6 = S.size . (!! 6) . iterate (update (==3) (`notElem` [2, 3]))
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main = runAoC (toIndices . lines) (run6 . S.fromList . map extendIndex) (run6 . S.fromList . map (extendIndex . extendIndex))
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where toIndices input = [V.fromTuple (row, col) :: Vector 2 Int | (row, line) <- zip [0..] input, (col, '#') <- zip [0..] line]
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extendIndex = V.cons 0
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