AoC/2019/day12/day12.hs

import Data.List.Split
import Data.List
import Linear.V3

main :: IO ()
main = do
    moons <- parseContent <$> readFile "input"
    let velocity = replicate 4 [0,0,0]
    print $ part1 (toV3 moons, toV3 velocity)
    print $ part2 (moons,velocity)

part1 :: ([V3 Int],[V3 Int]) -> Int
part1 x = energy $ iterate step x !! 1000

--I’m sure there is a better way to do this
toV3 :: [[Int]] -> [V3 Int]
toV3 = map (\[x,y,z]->V3 x y z)

parseContent :: String -> [[Int]]
parseContent = map (map read . splitOn ",") . lines . removeJunk
    where removeJunk xs = [ x | x <- xs, x `notElem` " <>xyz=" ]

step :: (Num a, Eq a) => ([a],[a]) -> ([a],[a])
step (moons,vel) = (zipWith (+) moons newVel,newVel)
    where dVel = gravity moons
          newVel = zipWith (+) vel dVel
          gravity xs = [sum [signum $ x-y | x<-xs, y/=x] | y<-xs]

energy :: ([V3 Int],[V3 Int]) -> Int
energy (x,y) = sum $ zipWith (*) (geten x) (geten y) where
    geten = map (sum . abs)

findPeriod :: (Num a, Eq a) => ([a], [a]) -> ([a], [a]) -> Int -> Int
findPeriod x a n = if x'==a then n else findPeriod x' a (n+1)
    where x' = step x

part2 :: (Num a, Eq a) => ([[a]], [[a]]) -> Int
part2 (moons,vel) = lcm' periods
    where m = transpose moons
          v = transpose vel
          periods = zipWith (curry findPeriod') m v
          findPeriod' x = findPeriod x x 1

lcm' :: [Int] -> Int
lcm' xs = product $ zipWith (^) nums maxElems
    where nums = nub $ concat decomp
          decomp = map decomposition xs
          maxElems = [maximum $ map (length . elemIndices x) decomp | x<-nums]

--hyper optimized prime decomposition
decomposition :: Int -> [Int]
decomposition 1 = []
decomposition x =
  let n =
        if x `mod` 2 == 0
          then 2
          else 3
      maxiter = (floor . (sqrt :: Double -> Double) . fromIntegral) x
      findprim candidate current
        | (candidate <= maxiter) && (x `mod` candidate /= 0) =
          findprim (next current) (current + 1)
        | otherwise = candidate
      m = findprim n 1
   in if m <= maxiter
        then m : decomposition (x `div` m)
        else [x]
  where
    next k = k * 4 - k `div` 2 * 2 + 1