From 5e171b20c0099ca7eebd5e67bacf089b9a59119a Mon Sep 17 00:00:00 2001
From: shu <shu@lain.localdomain>
Date: Thu, 12 Dec 2019 10:55:24 +0100
Subject: [PATCH] Day 12 Part 1

---
 2019/day12/day12.hs | 68 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 54 insertions(+), 14 deletions(-)

diff --git a/2019/day12/day12.hs b/2019/day12/day12.hs
index 76b56d9..5b4e8a4 100644
--- a/2019/day12/day12.hs
+++ b/2019/day12/day12.hs
@@ -1,28 +1,68 @@
-{-# LANGUAGE LambdaCase #-}
-
 import Data.List.Split
+import Data.List
 import Linear.V3
 
+main :: IO ()
 main = do
-    moons <- parseContent <$> readFile "testinput"
-    let velocity = replicate 4 $ V3 0 0 0
-    print $ energy $ step (moons,velocity) 1000
+    moons <- parseContent <$> readFile "input"
+    let velocity = replicate 4 [0,0,0]
+    print $ part1 (toV3 moons, toV3 velocity)
+    print $ part2 (moons,velocity)
 
-removeJunk :: String -> String
-removeJunk xs = [ x | x <- xs, x `notElem` " <>xyz=" ]
+part1 :: ([V3 Int],[V3 Int]) -> Int
+part1 x = energy $ iterate step x !! 1000
 
-parseContent :: String -> [V3 Int]
-parseContent = map ((\[x,y,z]->V3 x y z) . map read . splitOn ",") . lines . removeJunk
+--I’m sure there is a better way to do this
+toV3 :: [[Int]] -> [V3 Int]
+toV3 = map (\[x,y,z]->V3 x y z)
 
-gravity :: [V3 Int] -> [V3 Int]
-gravity xs = [sum [signum $ x-y | x<-xs, y/=x] | y<-xs]
+parseContent :: String -> [[Int]]
+parseContent = map (map read . splitOn ",") . lines . removeJunk
+    where removeJunk xs = [ x | x <- xs, x `notElem` " <>xyz=" ]
 
-step :: ([V3 Int],[V3 Int]) -> Int -> ([V3 Int],[V3 Int])
-step (moons,vel) 0 = (moons,vel)
-step (moons,vel) n = step (zipWith (+) moons newVel,newVel) (n-1)
+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