2 files changed, 119 insertions, 1 deletions
diff --git a/2023/20-Pulse_Propagation/first.hs b/2023/20-Pulse_Propagation/first.hs
index c43e332..8704be9 100644
--- a/2023/20-Pulse_Propagation/first.hs
+++ b/2023/20-Pulse_Propagation/first.hs
@@ -61,7 +61,6 @@ compute input = let (x, y) = computeX 1000 (0, 0) $ initConjuctions input in x *
     computeX i n input = let (n', input') = compute' (1, 0) [("button", Low, "broadcaster")] input
                          in computeX (i-1) (scoreAdd n n') input'
     compute' :: (Int, Int) -> [(String, Pulse, String)] -> Input -> ((Int, Int), Input)
-    compute' n [] input = (n, input)
     compute' n signals input | length stepAll == 0 = (n, input)
                              | otherwise = compute' (scoreAdd n $ score stepAll) stepAll alterAll
       where
diff --git a/2023/20-Pulse_Propagation/second.hs b/2023/20-Pulse_Propagation/second.hs
new file mode 100644
index 0000000..5eaf39e
--- /dev/null
+++ b/2023/20-Pulse_Propagation/second.hs
@@ -0,0 +1,119 @@
+-- requires cabal install --lib megaparsec parser-combinators heap vector
+module Main (main) where
+
+import           Control.Applicative.Permutations
+import           Control.Monad                    (void, when)
+import qualified Data.Char                        as C
+import           Data.Either
+import           Data.Functor
+import qualified Data.Heap                        as H
+import qualified Data.List                        as L
+import qualified Data.Map                         as M
+import           Data.Maybe
+import qualified Data.Set                         as S
+import qualified Data.Vector                      as V
+import qualified Data.Vector.Unboxed              as VU
+import           Data.Void                        (Void)
+import           Text.Megaparsec
+import           Text.Megaparsec.Char
+
+import           Debug.Trace
+
+data Pulse = Low | High deriving (Eq, Show)
+data Module = Normal | FlipFlop Bool | Conjunction (M.Map String Pulse) | Broadcaster deriving (Eq, Show)
+data Configuration = Configuration Module String [String] deriving (Eq, Show)
+type Conf = (Module, [String])
+type Input = M.Map String Conf
+
+type Parser = Parsec Void String
+
+parseModule :: Parser Module
+parseModule = char '%' $> FlipFlop False
+          <|> char '&' $> Conjunction M.empty
+          <|> lookAhead (string "broadcaster") $> Broadcaster
+          <|> lookAhead letterChar $> Normal
+
+parseLabel :: Parser String
+parseLabel = some letterChar
+
+parseConfiguration :: Parser Configuration
+parseConfiguration = Configuration <$> parseModule
+                                   <*> parseLabel <* string " -> "
+                                   <*> some (parseLabel <* optional (string ", "))
+
+parseInput' :: Parser Input
+parseInput' = M.fromList . map (\(Configuration m s l) -> (s, (m, l))) <$> some (parseConfiguration <* eol) <* eof
+
+parseInput :: String -> IO Input
+parseInput filename = do
+  input <- readFile filename
+  case runParser parseInput' filename input of
+    Left bundle  -> error $ errorBundlePretty bundle
+    Right input' -> return input'
+
+compute :: Input -> Int
+compute input = L.foldl' lcm 1 $ computeX 0 (take (length targets) $ repeat Nothing) $ initConjuctions input
+  where
+    computeX :: Int -> [Maybe Int] -> Input -> [Int]
+    computeX i acc input | all isJust acc = fromJust <$> acc
+                         | otherwise = let (acc', input') = compute' [("button", Low, "broadcaster")] i acc input
+                                       in computeX (i+1) acc' input'
+    compute' :: [(String, Pulse, String)] -> Int -> [Maybe Int] -> Input -> ([Maybe Int], Input)
+    compute' signals i acc input | length stepAll == 0 = (acc, input)
+                                 | otherwise = let acc' = map (accStep i stepAll) $ L.zip targets acc
+                                               in compute' stepAll i acc' alterAll
+      where
+        alterAll :: Input
+        alterAll = L.foldl' alterOne input signals
+        alterOne :: Input -> (String, Pulse, String) -> Input
+        alterOne acc (prev, p, me) = alter p prev me acc (M.lookup me input)
+        alter :: Pulse -> String -> String -> Input -> Maybe Conf -> Input
+        alter _    _    _  input (Just (Normal, _))         = input
+        alter High _    _  input (Just (FlipFlop _, _))     = input
+        alter Low  _    me input (Just (FlipFlop False, l)) = M.insert me (FlipFlop True, l) input
+        alter Low  _    me input (Just (FlipFlop True, l))  = M.insert me (FlipFlop False, l) input
+        alter p    prev me input (Just (Conjunction m, l))  = M.insert me (Conjunction $ M.insert prev p m, l) input
+        alter p    _    _  input (Just (Broadcaster, l))    = input
+        alter _    _    _  input Nothing                    = input
+        stepAll :: [(String, Pulse, String)]
+        stepAll = L.foldl' stepOne [] signals
+        stepOne :: [(String, Pulse, String)] -> (String, Pulse, String) -> [(String, Pulse, String)]
+        stepOne acc (prev, p, s) = step p prev s acc (M.lookup s input)
+        step :: Pulse -> String -> String -> [(String, Pulse, String)] -> Maybe Conf -> [(String, Pulse, String)]
+        step _    _    _  acc (Just (Normal, _))         = acc
+        step High _    _  acc (Just (FlipFlop _, _))     = acc
+        step Low  _    me acc (Just (FlipFlop False, l)) = acc ++ map (set me High) l
+        step Low  _    me acc (Just (FlipFlop True, l))  = acc ++ map (set me Low) l
+        step p    prev me acc (Just (Conjunction m, l))  = let p2 = if length (M.filter (\x -> x == High) $ M.insert prev p m) == length m then Low else High
+                                                           in acc ++ map (set me p2) l
+        step p    _    me acc (Just (Broadcaster, l))    = acc ++ map (set me p) l
+        step _    _    _  acc Nothing                    = acc
+    initConjuctions :: Input -> Input
+    initConjuctions input = let r = M.foldrWithKey initConf input input in r
+    initConf :: String -> Conf -> Input -> Input
+    initConf c (_, l) input = L.foldl' initOne input l
+      where
+        initOne :: Input -> String -> Input
+        initOne input s = case M.lookup s input of
+          Just (Conjunction m, l) -> M.insert s (Conjunction (M.insert c Low m), l) input
+          _ -> input
+    set :: String -> Pulse -> String -> (String, Pulse, String)
+    set me p s = (me, p, s)
+    targets = pointsTo toRx
+    [toRx] = pointsTo "rx"
+    pointsTo :: String -> [String]
+    pointsTo name = L.foldl' (\acc (k, (_, l)) -> if isJust (L.elemIndex name l) then k:acc else acc) [] $ M.assocs input
+    accStep :: Int -> [(String, Pulse, String)] -> (String, Maybe Int) -> Maybe Int
+    accStep _ _ (_, Just x) = Just x
+    accStep i stepAll (t, Nothing) | triggered = Just (i + 1)
+                                   | otherwise = Nothing
+      where
+        triggered = L.foldl' (trigg t) False stepAll
+        trigg _ True _            = True
+        trigg t False (_, Low, u) = t == u
+        trigg _ _ _               = False
+
+main :: IO ()
+main = do
+  input <- parseInput "input"
+  print $ compute input