98 lines
2.6 KiB
Haskell
98 lines
2.6 KiB
Haskell
{-# LANGUAGE LambdaCase #-}
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{-# LANGUAGE BangPatterns #-}
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{-# LANGUAGE ParallelListComp #-}
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import Data.List as L
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import Data.Maybe
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import Data.Ord
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import Data.Ratio
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import qualified Data.Vector as V
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type Asteroid_old = (Int, Int)
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data Asteroid =
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Asteroid Int Int
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deriving (Show)
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instance Eq Asteroid where
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Asteroid a b == Asteroid c d = reduce a b == reduce c d
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where
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reduce x y
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| y == 0 && x == 0 = (0, 0)
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| x == 0 = (0, signum y)
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| y == 0 = (signum x, 0)
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| otherwise =
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(signum x * (abs $numerator z), signum y * (abs $denominator z))
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where
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z = x %y
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instance Ord Asteroid where
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Asteroid a b `compare` Asteroid c d = (phi a b) `compare` (phi c d)
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where
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phi x y = phi' (fromIntegral x) (fromIntegral y)
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phi' :: Double -> Double -> Double
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phi' x y
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| x >= 0 = atan2 x (-y)
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| otherwise = 2 * pi + atan2 (-x) y
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(+|) :: Asteroid -> Asteroid -> Asteroid
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(+|) (Asteroid a b) (Asteroid c d) = Asteroid (a + c) (b + d)
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(-|) :: Asteroid -> Asteroid -> Asteroid
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(-|) (Asteroid a b) (Asteroid c d) = Asteroid (a - c) (b - d)
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neg :: Asteroid -> Asteroid
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neg (Asteroid a b) = Asteroid (-a) (-b)
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dist :: Asteroid -> Int
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dist (Asteroid x y) = abs x + abs y
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main = do
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content <- lines <$> readFile "input"
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print $ parse content
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let aMax = fst $ maxInSight $ parse content
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print aMax
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let newlist =
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listCycle $
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sort $
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sortOn (dist . fromJust) $
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snd $ transformCoordinates (parse content) aMax
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let newnewlist = snd $ transformCoordinates newlist (neg aMax)
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print $ newnewlist !! 199
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listCycle :: [Maybe Asteroid] -> [Maybe Asteroid]
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listCycle [] = []
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listCycle xs = nub xs ++ listCycle (xs \\ nub xs)
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parse :: [String] -> [Maybe Asteroid]
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parse =
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concat .
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V.toList . V.map V.toList . toAsteroids . V.map V.fromList . V.fromList
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where
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toAsteroids = V.imap g
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g x = V.imap (f x)
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f i j a =
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case a of
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'.' -> Nothing
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_ -> Just $ Asteroid j i
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transformCoordinates ::
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[Maybe Asteroid] -> Asteroid -> (Asteroid, [Maybe Asteroid])
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transformCoordinates xs a = (a, [Just $ x -| a | Just x <- xs, x /= a])
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maxInSight :: [Maybe Asteroid] -> (Asteroid, Int)
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maxInSight xs =
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maximumBy (comparing snd) $ map (f . transformCoordinates xs) (catMaybes xs)
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where
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f (x, y) = (x, pred . length . nub $ y)
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asts :: [String] -> [Maybe Asteroid_old]
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asts xxs =
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L.nub
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[ if (xxs !! y) !! (x) == '.'
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then Nothing
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else Just (x, y)
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| y <- [0 .. (L.length $ L.head xxs) - 1]
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, x <- [0 .. L.length xxs - 1]
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]
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