Day 12: lcm is in Prelude :veryironicwow:

2019/day12/day12.hs

@@ -1,6 +1,7 @@
 import Data.List
 import Data.List.Split
 import Linear.V3
+
 main :: IO ()
 main = do
   moons <- parseContent <$> readFile "input"
@@ -30,9 +31,8 @@ step (moons, vel) = (zipWith (+) moons newVel, newVel)
     newVel = zipWith (+) vel dVel
     gravity xs = [sum [signum $ x - y | x <- xs, y /= x] | y <- xs]
 
-
 part2 :: (Num a, Eq a) => ([[a]], [[a]]) -> Int
-part2 (moons, vel) = lcm' periods
+part2 (moons, vel) = foldr1 lcm periods
   where
     m = transpose moons
     v = transpose vel
@@ -46,30 +46,3 @@ findPeriod x a n =
     else findPeriod x' a (n + 1)
   where
     x' = step x
-
-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