Day 15, part 1 and 2: slow solution

day15/main.hs

@@ -11,6 +11,63 @@
 import Debug.Trace (trace)
 import Text.Pretty.Simple
 
+import Data.IntMap.Strict (IntMap)
+import qualified Data.IntMap.Strict as I
+
+import Data.Maybe (fromMaybe)
+import Data.List (iterate')
+
+exampleInput1 :: [Int]
+exampleInput1 = [0,3,6]
+
+exampleInput2 :: [Int]
+exampleInput2 = [1,3,2]
+exampleInput3 :: [Int]
+exampleInput3 = [3,1,2]
+
+input :: [Int]
+input = [0,3,1,6,7,5]
+
+type Turn = Int
+type Number = Int
+
+
+-- Each Number is attached to the last Turn it was seen
+-- The current Turn is recorded too
+-- Last spoken Number is recorded too
+data Game = Game { unMem :: (IntMap Turn)
+                 , unTurn :: Turn
+                 , unNumber :: Number
+                 }
+  deriving Show
+
+initGame :: [Int] -> Game
+initGame keys = Game mem ((length keys) + 1) 0
+  where
+    mem = I.fromList (zip keys [1..])
+
+next :: Game -> Game
+next (Game mem turn n) = fromMaybe (Game (I.insert n turn mem) (turn+1) 0) $ do
+  lastTurn <- I.lookup n mem
+  pure $ Game (I.insert n turn mem) (turn+1) (turn - lastTurn)
+
 main :: IO ()
 main = do
+  putStrLn ":: Day 15 - Tests 1"
+  print exampleInput1
+  putStrLn $ "turn 04: " <> (show $ initGame exampleInput1)
+  putStrLn $ "turn 05: " <> (show $ next $ initGame exampleInput1)
+  putStrLn $ "turn 06: " <> (show $ next $ next $ initGame exampleInput1)
+  putStrLn $ "turn 07: " <> (show $ next $ next $ next $ initGame exampleInput1)
+  putStrLn $ "turn 08: " <> (show $ next $ next $ next $ next $ initGame exampleInput1)
+  putStrLn $ "turn 09: " <> (show $ next $ next $ next $ next $ next $ initGame exampleInput1)
+  putStrLn $ "turn 10: " <> (show $ next $ next $ next $ next $ next $ next $ initGame exampleInput1)
+  print $ last $ take 2017 $ map unNumber $ iterate next $ initGame exampleInput1
+  print $ last $ take 2017 $ map unNumber $ iterate next $ initGame exampleInput2
+  print $ last $ take 2017 $ map unNumber $ iterate next $ initGame exampleInput3
   putStrLn ":: Day 15 - Part 1"
+  print $ last $ take (2020 - 6) $ map unNumber $ iterate next $ initGame input
+  putStrLn ":: Day 15 - Part 2"
+  -- print $ last $ take (30000000 - 3) $ map unNumber $ iterate' next $ initGame exampleInput1
+  print $ last $ take (30000000 - 6) $ map unNumber $ iterate' next $ initGame input
+