1 files changed, 84 insertions, 0 deletions
diff --git a/2017/18.hs b/2017/18.hs
new file mode 100644
index 0000000..a803906
--- /dev/null
+++ b/2017/18.hs
@@ -0,0 +1,84 @@
+import Control.Monad
+import Data.Char
+import Data.Maybe
+import qualified Data.Map.Strict as Map
+
+data Ref = Reg Char | Num Int
+  deriving Show
+
+data Ins = Set Char Ref | Add Char Ref | Mul Char Ref | Mod Char Ref | Snd Ref | Rcv Char | Jgz Ref Ref
+  deriving Show
+
+parseRef :: String -> Ref
+parseRef str = if all (\c -> isDigit c || c == '-') str then Num (read str) else Reg (head str)
+
+parse :: String -> Ins
+parse str = case words str of
+    ["set", [d], s] -> Set d (parseRef s)
+    ["add", [d], s] -> Add d (parseRef s)
+    ["mul", [d], s] -> Mul d (parseRef s)
+    ["mod", [d], s] -> Mod d (parseRef s)
+    ["snd", r] -> Snd (parseRef r)
+    ["rcv", [d]] -> Rcv d
+    ["jgz", c, t] -> Jgz (parseRef c) (parseRef t)
+    _ -> undefined
+
+get :: Ref -> Map.Map Char Int -> Int
+get (Num i) _ = i
+get (Reg c) vmap = fromMaybe 0 (Map.lookup c vmap)
+
+exec1 :: [Ins] -> Int
+exec1 inss' = go inss' 0 Map.empty 0
+  where
+    go :: [Ins] -> Int -> Map.Map Char Int -> Int -> Int
+    go inss idx vmap snd
+        | idx < 0 = undefined
+        | idx >= length inss = undefined
+        | otherwise = case inss !! idx of
+            Set d ref -> go inss (idx+1) (Map.insert d (get ref vmap) vmap) snd
+            Add d ref -> go inss (idx+1) (Map.insert d (get (Reg d) vmap + get ref vmap) vmap) snd
+            Mul d ref -> go inss (idx+1) (Map.insert d (get (Reg d) vmap * get ref vmap) vmap) snd
+            Mod d ref -> go inss (idx+1) (Map.insert d (get (Reg d) vmap `mod` get ref vmap) vmap) snd
+            Snd ref -> go inss (idx+1) vmap (get ref vmap)
+            Rcv d -> if get (Reg d) vmap == 0 then go inss (idx+1) vmap snd else snd
+            Jgz cd tg -> go inss (idx + if get cd vmap > 0 then get tg vmap else 1) vmap snd
+
+data State = State [Ins] Int (Map.Map Char Int) [Int]
+  deriving Show
+
+makeState :: [Ins] -> Int -> State
+makeState inss pid = State inss 0 (Map.fromList [('p', pid)]) []
+
+supplyInput :: State -> [Int] -> State
+supplyInput (State inss idx vmap inp) input = State inss idx vmap (inp ++ input)
+
+exec2 :: State -> (State, [Int])
+exec2 state@(State inss idx vmap inp)
+    | idx < 0 = (state, [])
+    | idx >= length inss = (state, [])
+    | otherwise = case inss !! idx of
+        Set d ref -> exec2 $ State inss (idx+1) (Map.insert d (get ref vmap) vmap) inp
+        Add d ref -> exec2 $ State inss (idx+1) (Map.insert d (get (Reg d) vmap + get ref vmap) vmap) inp
+        Mul d ref -> exec2 $ State inss (idx+1) (Map.insert d (get (Reg d) vmap * get ref vmap) vmap) inp
+        Mod d ref -> exec2 $ State inss (idx+1) (Map.insert d (get (Reg d) vmap `mod` get ref vmap) vmap) inp
+        Snd ref -> fmap (get ref vmap :) $ exec2 $ State inss (idx+1) vmap inp
+        Rcv d -> case inp of
+            [] -> (state, [])
+            x:xs -> exec2 $ State inss (idx+1) (Map.insert d x vmap) xs
+        Jgz cd tg -> exec2 $ State inss (idx + if get cd vmap > 0 then get tg vmap else 1) vmap inp
+
+parallel :: State -> State -> Int
+parallel state0 state1 =
+    let (state0', out0) = exec2 state0
+        (state1', out1) = exec2 (supplyInput state1 out0)
+        state0'' = supplyInput state0' out1
+    in if null out0 && null out1
+        then 0
+        else length out1 + parallel state0'' state1'
+
+main :: IO ()
+main = do
+    input <- liftM (map parse . lines) (readFile "18.in")
+    print (exec1 input)
+
+    print $ parallel (makeState input 0) (makeState input 1)