1 files changed, 67 insertions, 0 deletions
diff --git a/Day10/app/Main.hs b/Day10/app/Main.hs
new file mode 100644
index 0000000..5647726
--- /dev/null
+++ b/Day10/app/Main.hs
@@ -0,0 +1,67 @@
+module Main (main) where
+
+import System.Environment ( getArgs )
+import Text.Read (readMaybe)
+import Data.Bifunctor (bimap)
+
+main :: IO ()
+main = getArgs >>= readFile . head >>= putStr . solveDay10
+
+solveDay10 :: String -> String
+solveDay10 = formatDay10Result . fmap solveDay10Parts . parseDay10Input
+
+formatDay10Result :: Either String (Int, String) -> String
+formatDay10Result (Left s) = s
+formatDay10Result (Right (p1, p2)) = "Part 1: " ++ show p1 ++ "\n\nPart 2:\n" ++ p2
+
+data Command = NoOp | AddX Int
+
+parseDay10Input :: String -> Either String [Command]
+parseDay10Input = mapM parseCommand . lines
+
+parseCommand :: String -> Either String Command
+parseCommand "noop" = Right NoOp
+parseCommand ('a':'d':'d':'x':' ':ss) =  maybe (Left "Invalid parameter for addx instruction") (Right . AddX) $ readMaybe ss 
+parseCommand x = Left $ "Unknown instruction: " ++ x
+
+solveDay10Parts :: [Command] -> (Int, String)
+solveDay10Parts = bimap solveDay9Part1 solveDay9Part2 . dup
+    where dup x = (x,x)
+
+newtype CycleCount = CycleCount Int deriving (Eq, Ord)
+newtype RegisterValue = RegisterValue Int
+newtype SignalStrength = SignalStrength Int
+newtype CpuState = CpuState (CycleCount, RegisterValue)
+
+unSignalStrength :: SignalStrength -> Int
+unSignalStrength (SignalStrength a) = a
+
+signalStrength :: CycleCount -> RegisterValue -> SignalStrength
+signalStrength (CycleCount c) (RegisterValue r) = SignalStrength (c*r)
+
+getRegisterValue :: CpuState -> RegisterValue
+getRegisterValue (CpuState (_,r)) = r
+
+solveDay9Part1 :: [Command] -> Int 
+solveDay9Part1 = getSumOfRelevantSignalStrengths . cpuStates
+
+cpuStates :: [Command] -> [CpuState] -- this could be solved using scanl, but the problem is easier to solve using a dedicated worker function.
+cpuStates = cpuStatesWorker (CpuState (CycleCount 1, RegisterValue 1)) 
+
+cpuStatesWorker :: CpuState -> [Command] -> [CpuState]
+cpuStatesWorker c [] = return c
+cpuStatesWorker (CpuState (CycleCount c, r)) (NoOp:cs) = cpuStatesWorker (CpuState (CycleCount (c+1), r)) cs
+cpuStatesWorker (CpuState (CycleCount c, RegisterValue r)) ((AddX x):cs) = newState:cpuStatesWorker newState cs
+    where newState = CpuState (CycleCount (c+2), RegisterValue (r+x))
+
+getSumOfRelevantSignalStrengths :: [CpuState] -> Int
+getSumOfRelevantSignalStrengths s = sum $ map (unSignalStrength . getSignalStrengthAtCycleCount s . CycleCount) $ take 6 $ iterate (+40) 20
+
+getSignalStrengthAtCycleCount :: [CpuState] -> CycleCount -> SignalStrength
+getSignalStrengthAtCycleCount s c = signalStrength c $ getRegisterAtCycleCount s c
+
+getRegisterAtCycleCount :: [CpuState] -> CycleCount -> RegisterValue
+getRegisterAtCycleCount s c = getRegisterValue $ last $ takeWhile (\(CpuState (cc,_)) -> cc <= c) s
+
+solveDay9Part2 :: [Command] -> String
+solveDay9Part2 c = "Not yet done, sorry.\n"
+\ No newline at end of file