115 lines
2.8 KiB
Haskell
115 lines
2.8 KiB
Haskell
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{-# LANGUAGE FlexibleContexts #-}
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import qualified Data.Vector as V
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import Text.Parsec
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data Op = Acc Int
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| Jmp Int
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| Nop Int
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deriving Show
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main :: IO ()
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main = do
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raw <- readFile "day8.txt"
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let ops = V.fromList $ zip (repeat False)
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$ validate $ map (parse lineP []) $ lines raw
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ansA = solveA ops
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ansB = solveB ops
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in do
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putStrLn $ "day7a: " ++ (show ansA)
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putStrLn $ "day7b: " ++ (show ansB)
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solveA :: V.Vector (Bool, Op) -> Int
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solveA ops = runMachineA ops 0 0
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solveB :: V.Vector (Bool, Op) -> Int
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solveB ops = case testSwaps ops 0 of
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Nothing -> error "unsolvable?"
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Just x -> x
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runMachineA :: V.Vector (Bool, Op) -> Int -> Int -> Int
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runMachineA ops pc ac = do
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let (check,op) = ops V.! pc
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in case check of
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True -> ac
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_ -> do
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let nac = case op of
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(Acc x) -> ac + x
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_ -> ac
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npc = case op of
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(Jmp y) -> pc + y
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_ -> succ pc
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nops = ops V.// [(pc, (True, op))]
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in runMachineA nops npc nac
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swapOp :: V.Vector (Bool, Op) -> Int -> Maybe (V.Vector (Bool, Op))
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swapOp ops ind =
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case op of
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(Acc _) -> Nothing
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(Nop x) -> Just $ ops V.// [(ind, (check, Jmp x))]
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(Jmp x) -> Just $ ops V.// [(ind, (check, Nop x))]
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where
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(check,op) = ops V.! ind
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testSwaps :: V.Vector (Bool, Op) -> Int -> Maybe Int
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testSwaps ops ind
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| ind >= V.length ops = Nothing
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| otherwise =
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case res of
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Nothing -> testSwaps ops $ succ ind
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(Just nops) -> case (runMachineB nops 0 0) of
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Nothing -> testSwaps ops $ succ ind
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x -> x
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where
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res = swapOp ops ind
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runMachineB :: V.Vector (Bool, Op) -> Int -> Int -> Maybe Int
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runMachineB ops pc ac =
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if pc == V.length ops
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then Just ac
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else do
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let (check,op) = ops V.! pc
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in case check of
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True -> Nothing
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_ -> do
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let nac = case op of
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(Acc x) -> ac + x
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_ -> ac
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npc = case op of
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(Jmp y) -> pc + y
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_ -> succ pc
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nops = ops V.// [(pc, (True, op))]
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in runMachineB nops npc nac
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validate :: [Either ParseError Op] -> [Op]
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validate [] = []
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validate ((Left _):_) = error "invalid input"
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validate ((Right b):bs) = b:(validate bs)
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lineP :: Parsec String () Op
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lineP = do
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o <- opP
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whitespaces
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i <- intP
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whitespaces
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eof
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return $ o i
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intP :: Parsec String () Int
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intP = do
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s <- oneOf ['+','-']
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v <- many1 digit
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return $ (if s == '-' then -1 else 1) * (read v)
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opP :: Parsec String () (Int -> Op)
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opP = do
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o <- (string "acc") <|> (string "jmp") <|> (string "nop")
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case o of
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"acc" -> return Acc
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"jmp" -> return Jmp
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_ -> return Nop
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whitespaces :: Parsec String () String
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whitespaces = many $ char ' '
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