--- /dev/null
+import Text.Parsec hiding (State)
+import Text.ParserCombinators.Parsec.Number
+-- import Control.Applicative ((<*), (*>), (<*>))
+import Data.Maybe (fromJust)
+import Data.List (elemIndex)
+
+import Control.Monad.Identity
+import Control.Monad.State
+import Control.Monad.Writer
+
+data Instruction = SwapPosition Int Int
+ | SwapLetter Char Char
+ | RotateSteps Int
+ | RotateLetter Char
+ | Reverse Int Int
+ | Move Int Int
+ deriving (Show, Eq)
+
+data Log = Log {
+ action :: String
+ } deriving (Show)
+
+data Password = Password {
+ password :: String
+ } deriving (Show)
+
+
+type App = WriterT [Log] (StateT Password Identity)
+
+infixl 9 ??
+
+(??) :: Eq a => [a] -> a -> Int
+(??) items item = fromJust $ elemIndex item items
+
+
+initial = "abcdefgh"
+final = "fbgdceah"
+
+testInstructions = "\
+\swap position 4 with position 0\n\
+\swap letter d with letter b\n\
+\reverse positions 0 through 4\n\
+\rotate left 1 step\n\
+\move position 1 to position 4\n\
+\move position 3 to position 0\n\
+\rotate based on position of letter b\n\
+\rotate based on position of letter d\n"
+
+main :: IO ()
+main = do
+ -- let ti = successfulParse $ parseIfile testInstructions
+ -- part1 ti "abcde"
+ -- part2 (reverse ti) "decab"
+ text <- readFile "advent21.txt"
+ let instructions = successfulParse $ parseIfile text
+ part1 instructions initial
+ part2 (reverse instructions) final
+
+part1 :: [Instruction] -> String -> IO ()
+part1 instructions start =
+ let state = Password {password = start}
+ in print $ runIdentity (runStateT (runWriterT (apply instructions)) state)
+ -- in putStrLn $ password $ runIdentity (execStateT (runWriterT (apply instructions)) state)
+
+part2 :: [Instruction] -> String -> IO ()
+part2 instructions end =
+ let state = Password {password = end}
+ in print $ runIdentity (runStateT (runWriterT (unApply instructions)) state)
+ -- in putStrLn $ password $ runIdentity (execStateT (runWriterT (apply instructions)) state)
+
+
+apply :: [Instruction] -> App ()
+apply [] = return ()
+apply (i:is) =
+ do st <- get
+ let p0 = password st
+ let p1 = applyInstruction i p0
+ put st {password = p1}
+ tell [Log (p0 ++ " -> " ++ p1 ++ " : " ++ (show i))]
+ apply is
+
+
+applyInstruction :: Instruction -> String -> String
+applyInstruction (SwapPosition from to) p0
+ | from == to = p0
+ | otherwise = prefix ++ [p0!!end] ++ midfix ++ [p0!!start] ++ suffix
+ where start = minimum [from, to]
+ end = maximum [from, to]
+ prefix = take start p0
+ midfix = take (end-start-1) $ drop (start+1) p0
+ suffix = drop (end+1) p0
+
+applyInstruction (SwapLetter l0 l1) p0 = applyInstruction (SwapPosition (p0??l0) (p0??l1)) p0
+
+applyInstruction (RotateSteps n) p0 = (drop n' p0) ++ (take n' p0)
+ where n' = if n < 0
+ then (-1 * n)
+ else (length p0) - n
+
+applyInstruction (RotateLetter l) p0 = applyInstruction (RotateSteps n) p0
+ where n = (1 + (p0??l) + if (p0??l) >= 4 then 1 else 0) `mod` (length p0)
+
+applyInstruction (Reverse from to) p0
+ | from == to = p0
+ | otherwise = prefix ++ (reverse midfix) ++ suffix
+ where start = minimum [from, to]
+ end = maximum [from, to]
+ prefix = take start p0
+ midfix = take (end-start+1) $ drop start p0
+ suffix = drop (end+1) p0
+
+applyInstruction (Move from to) p0
+ | from == to = p0
+ | otherwise = prefix ++ [p0!!from] ++ suffix
+ where without = take from p0 ++ drop (from+1) p0
+ prefix = take to without
+ suffix = drop (to) without
+
+
+unApply :: [Instruction] -> App ()
+unApply [] = return ()
+unApply (i:is) =
+ do st <- get
+ let p0 = password st
+ let p1 = unApplyInstruction i p0
+ put st {password = p1}
+ tell [Log (p1 ++ " <- " ++ p0 ++ " : " ++ (show i))]
+ unApply is
+
+unApplyInstruction :: Instruction -> String -> String
+unApplyInstruction (SwapPosition from to) p0 = applyInstruction (SwapPosition from to) p0
+unApplyInstruction (SwapLetter l0 l1) p0 = applyInstruction (SwapLetter l0 l1) p0
+unApplyInstruction (RotateSteps n) p0 = applyInstruction (RotateSteps (-1 * n)) p0
+unApplyInstruction (Reverse from to) p0 = applyInstruction (Reverse from to) p0
+unApplyInstruction (Move from to) p0 = applyInstruction (Move to from) p0
+unApplyInstruction (RotateLetter l) p0 = applyInstruction (RotateSteps n) p0
+ where n = case (p0??l) of
+ 0 -> -1
+ 1 -> -1
+ 2 -> 2
+ 3 -> -2
+ 4 -> 1
+ 5 -> -3
+ 6 -> 0
+ 7 -> -4
+ -- where n = case (p0??l) of
+ -- 0 -> -1
+ -- 1 -> -1
+ -- 2 -> 1
+ -- 3 -> -2
+ -- 4 -> 1
+
+
+instructionFile = instructionLine `endBy` newline
+instructionLine = choice [ swapL
+ , rotateL
+ , reverseL
+ , moveL
+ ]
+
+swapL = (try (string "swap ")) *> (swapPosL <|> swapLetterL)
+
+swapPosL = SwapPosition <$> (string "position" *> spaces *> int)
+ <*> (spaces *> string "with position" *> spaces *> int)
+
+swapLetterL = SwapLetter <$> (string "letter" *> spaces *> letter)
+ <*> (spaces *> string "with letter" *> spaces *> letter)
+
+rotateL = (try (string "rotate ")) *> (rotateDirL <|> rotateLetterL)
+
+rotateDirL = rotateStepify <$> ((string "left") <|> (string "right"))
+ <*> (spaces *> int <* spaces <* skipMany letter)
+ where rotateStepify dir n = case dir of
+ "left" -> (RotateSteps (-1 * n))
+ "right" -> (RotateSteps n)
+rotateLetterL = RotateLetter <$> (string "based on position of letter " *> letter)
+
+reverseL = Reverse <$> (string "reverse positions" *> spaces *> int)
+ <*> (spaces *> (string "through") *> spaces *> int)
+
+moveL = Move <$> (string "move position" *> spaces *> int)
+ <*> (spaces *> (string "to position") *> spaces *> int)
+
+
+parseIfile :: String -> Either ParseError [Instruction]
+parseIfile input = parse instructionFile "(unknown)" input
+
+parseIline :: String -> Either ParseError Instruction
+parseIline input = parse instructionLine "(unknown)" input
+
+successfulParse :: Either ParseError [a] -> [a]
+successfulParse (Left _) = []
+successfulParse (Right a) = a
projects / advent-of-code-16.git / blobdiff