78 lines
2.1 KiB
Haskell
78 lines
2.1 KiB
Haskell
import Data.List
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import Data.List.Split
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import Linear.V3
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main :: IO ()
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main = do
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moons <- parseContent <$> readFile "input"
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let velocity = replicate 4 [0, 0, 0]
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print $ part1 (toV3 moons, toV3 velocity)
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print $ part2 (moons, velocity)
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part1 :: ([V3 Int], [V3 Int]) -> Int
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part1 x = energy $ iterate step x !! 1000
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--I’m sure there is a better way to do this
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toV3 :: [[Int]] -> [V3 Int]
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toV3 = map (\[x, y, z] -> V3 x y z)
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parseContent :: String -> [[Int]]
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parseContent = map (map read . splitOn ",") . lines . removeJunk
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where
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removeJunk xs = [x | x <- xs, x `notElem` " <>xyz="]
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step :: (Num a, Eq a) => ([a], [a]) -> ([a], [a])
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step (moons, vel) = (zipWith (+) moons newVel, newVel)
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where
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dVel = gravity moons
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newVel = zipWith (+) vel dVel
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gravity xs = [sum [signum $ x - y | x <- xs, y /= x] | y <- xs]
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energy :: ([V3 Int], [V3 Int]) -> Int
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energy (x, y) = sum $ zipWith (*) (geten x) (geten y)
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where
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geten = map (sum . abs)
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findPeriod :: (Num a, Eq a) => ([a], [a]) -> ([a], [a]) -> Int -> Int
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findPeriod x a n =
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if x' == a
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then n
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else findPeriod x' a (n + 1)
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where
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x' = step x
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part2 :: (Num a, Eq a) => ([[a]], [[a]]) -> Int
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part2 (moons, vel) = lcm' periods
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where
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m = transpose moons
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v = transpose vel
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periods = zipWith (curry findPeriod') m v
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findPeriod' x = findPeriod x x 1
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lcm' :: [Int] -> Int
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lcm' xs = product $ zipWith (^) nums maxElems
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where
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nums = nub $ concat decomp
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decomp = map decomposition xs
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maxElems = [maximum $ map (length . elemIndices x) decomp | x <- nums]
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--hyper optimized prime decomposition
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decomposition :: Int -> [Int]
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decomposition 1 = []
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decomposition x =
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let n =
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if x `mod` 2 == 0
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then 2
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else 3
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maxiter = (floor . (sqrt :: Double -> Double) . fromIntegral) x
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findprim candidate current
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| (candidate <= maxiter) && (x `mod` candidate /= 0) =
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findprim (next current) (current + 1)
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| otherwise = candidate
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m = findprim n 1
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in if m <= maxiter
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then m : decomposition (x `div` m)
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else [x]
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where
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next k = k * 4 - k `div` 2 * 2 + 1
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