day 11

11/solution.hs

@@ -0,0 +1,49 @@
+import Data.List
+import Data.Function.Memoize
+import Debug.Trace
+import Control.Parallel.Strategies
+
+traceOut :: Show a => a -> a
+traceOut x = (traceShow x x)
+
+addFirst :: [[a]] -> a -> [[a]]
+addFirst [] x = [[x]]
+addFirst (y:ys) x = ([x] ++ y) : ys
+
+split :: [Char] -> String -> [String]
+split _ [] = []
+split delims (x:xs)
+  | elem x delims = [[]] ++ split delims xs
+  | otherwise     = addFirst (split delims xs) x
+
+splitInput :: String -> [Int]
+splitInput = map read . split [' '] . head . split ['\n']
+
+solve1 :: [Int] -> Int
+solve1 = length . foldl (.) id (take 25 $ repeat (concat . map stoneStep))
+
+solve2 :: [Int] -> Int
+solve2 xs = sum $ ((map ((memoize2 stoneCount) 75) xs) `using` parList rseq)
+
+stoneStep :: Int -> [Int]
+stoneStep 0 = [1]
+stoneStep x
+  | (floor $ logBase 10 $ fromIntegral x) `rem` 2 == 1 = let d = ((\x -> x `div` 2) $ (+1) $ floor $ logBase 10 $ fromIntegral x) in [x `div` 10^d, x `rem` 10^d]
+  | otherwise                                          = [x*2024] 
+
+splitAtIndex :: Int -> [a] -> [[a]]
+splitAtIndex 0 xs = [[], xs]
+splitAtIndex a (x:xs) = addFirst (splitAtIndex (a-1) xs) x
+
+stoneCount :: Int -> Int -> Int
+stoneCount 0 = (\x -> 1)
+stoneCount n = sum . map (((memoize2 stoneCount)) (n-1)) . stoneStep
+
+main :: IO()
+main = do
+       fileinp <- readFile "input.txt"
+       let parsed = splitInput fileinp
+       let solved1 = solve1 parsed
+       let solved2 = solve2 parsed
+       print solved1
+       print solved2