1 files changed, 35 insertions, 0 deletions
diff --git a/2020/8.hs b/2020/8.hs
new file mode 100644
index 0000000..bc90351
--- /dev/null
+++ b/2020/8.hs
@@ -0,0 +1,35 @@
+module Main where
+
+import Data.Maybe (catMaybes)
+import qualified Data.Set as Set
+
+import Asm
+import Input
+
+
+main :: IO ()
+main = do
+    input <- getInput 8
+    let prog = programFrom (map parseIns input)
+
+    let nodupPredicate set state
+          | sIP state `Set.member` set = (set, True)
+          | sIP state == programLength prog = (set, True)
+          | otherwise = (Set.insert (sIP state) set, False)
+
+    print (sAcc (evalUntil nodupPredicate prog mempty initState))
+
+    let overriders = catMaybes
+            [case programGet prog i of
+               NOP a -> Just $ \j -> if j == i then Just (JMP a) else Nothing
+               JMP a -> Just $ \j -> if j == i then Just (NOP a) else Nothing
+               _     -> Nothing
+            | i <- [0 .. programLength prog - 1]]
+
+        results =
+            [state
+            | ovr <- overriders
+            , let state = evalUntil nodupPredicate (prog `withOverrider` ovr) mempty initState
+            , sIP state == programLength prog]
+
+    print (sAcc (head results))