154 lines
5.4 KiB
Idris
154 lines
5.4 KiB
Idris
import System.File.ReadWrite
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import Data.List
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import Data.String
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data Crate = C Char
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Show Crate where
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show (C c) = pack ['[', c, ']']
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parseCrate : String -> Maybe Crate
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parseCrate str = let str = unpack str in
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case str of
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('[' :: x :: ']' :: _) => Just (C x)
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_ => Nothing
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data Stacks = Stks (List (List Crate))
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Show Stacks where
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show (Stks stacks) =
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let longestStack = foldl max 0 . map length $ stacks
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stringStacks = map (extendFront longestStack " ") . map (map show) $ stacks
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lastLine = unwords . map (\x => " " ++ x ++ " ") . map show $ rangeFromTo 1 (length stacks)
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lineStacks = filter (/= "") . map unwords . transposeList longestStack $ stringStacks
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in joinBy "\n" $ (lineStacks ++ [lastLine])
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where extendFront : Nat -> a -> List a -> List a
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extendFront k x xs =
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if length xs < k
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then replicate (minus k (length xs)) x ++ xs
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else xs
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transposeList : Nat -> List (List a) -> List (List a)
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transposeList k xs =
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if any isNil xs
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then replicate k []
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else let firsts = map (take 1) xs
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rests = map (drop 1) xs
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in foldl (++) [] firsts :: transposeList k (assert_smaller xs rests)
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-- Chunk up a list
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chunk : Nat -> List a -> List (List a)
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chunk k [] = []
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chunk k xs = let (head, tail) = splitAt k xs in
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head :: chunk k tail
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-- Ensure a list of maybes is at least a specific length
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ensureLen : Nat -> List (Maybe a) -> List (Maybe a)
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ensureLen k [] = replicate k Nothing
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ensureLen 0 xs = xs
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ensureLen (S k) (x :: xs) = x :: ensureLen k xs
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-- Parse a list of stacks, this should be passed a list of lines including the line of numbers
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parseStacks : Nat -> List String -> Stacks
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parseStacks k [] = Stks $ replicate k []
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parseStacks k (x :: []) = parseStacks k []
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parseStacks k (x :: xs) = let (Stks bottom) = parseStacks k xs
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row = ensureLen k . map parseCrate . map pack . chunk 4 . unpack $ x
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in Stks $ zipWith parseStacksHelper row bottom
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where parseStacksHelper : Maybe Crate -> List Crate -> List Crate
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parseStacksHelper (Just crate) xs = crate :: xs
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parseStacksHelper Nothing xs = xs
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-- Get the tops of each stack
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tops : Stacks -> String
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tops (Stks xss) = pack . map (\(C c) => c) . catMaybes . map head' $ xss
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simple : String
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simple = """
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[D]
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[N] [C]
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[Z] [M] [P]
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1 2 3
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move 1 from 2 to 1
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move 3 from 1 to 3
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move 2 from 2 to 1
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move 1 from 1 to 2
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"""
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data Command = Cmd Nat Nat Nat
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Show Command where
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show (Cmd x y z) = (show x) ++ " " ++ (show (y + 1)) ++ "->" ++ (show (z + 1))
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-- Parse a command
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parseCommand : String -> Maybe Command
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parseCommand str =
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let nums : List Nat
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nums = catMaybes . map parsePositive . words $ str
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in case nums of
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[x, y, z] => Just (Cmd x (minus y 1) (minus z 1))
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_ => Nothing
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-- Apply a command to the stacks
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applyCommand : Command -> Bool -> Stacks -> Maybe Stacks
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applyCommand (Cmd count from to) multiple stacks =
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do (crates, removed) <- extractCrates count from stacks
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addCrates (if multiple then crates else reverse crates) to removed
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where extractCrates : Nat -> Nat -> Stacks -> Maybe ((List Crate), Stacks)
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extractCrates count from (Stks []) = Nothing
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extractCrates count 0 (Stks (x :: xs)) =
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if count > length x
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then Nothing
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else let (taken, rest) = splitAt count x in
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Just (taken, Stks (rest :: xs))
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extractCrates count (S k) (Stks (x :: xs)) =
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do (c, (Stks s)) <- extractCrates count k (Stks xs)
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Just (c, (Stks (x :: s)))
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addCrates : List Crate -> Nat -> Stacks -> Maybe Stacks
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addCrates xs to (Stks []) = Nothing
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addCrates xs 0 (Stks (x :: ys)) = Just (Stks ((xs ++ x) :: ys))
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addCrates xs (S k) (Stks (x :: ys)) =
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do (Stks added) <- addCrates xs k (Stks ys)
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Just (Stks (x :: added))
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data CmdResult = CR Bool (Maybe Command) Stacks
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Show CmdResult where
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show (CR bool command stacks) =
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unlines ["Command applied: " ++ (show bool), "Command: " ++ (show command), show stacks]
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-- Apply a list of commands to a stacks
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applyCommands : List Command -> Bool -> Stacks -> List CmdResult
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applyCommands [] multiple x = [CR False Nothing x]
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applyCommands (y :: xs) multiple x =
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case applyCommand y multiple x of
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Just stacks => CR True (Just y) stacks :: applyCommands xs multiple stacks
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Nothing => [CR False (Just y) x]
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mapM : Monad m => (a -> m b) -> List a -> m (List b)
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mapM f [] = pure []
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mapM f (x :: xs) =
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do x <- f x
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rest <- mapM f xs
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pure $ x :: rest
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partial unwrap : Maybe a -> a
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unwrap (Just x) = x
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partial main : IO ()
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main =
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do file <- readFile "input"
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case file of
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Right content =>
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let stacks = parseStacks 9 . takeWhile (/= "") . lines $ content
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commands = catMaybes . map parseCommand . drop 1 . dropWhile (/= "") . lines $ content
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part1 = unwrap . map (\(CR _ _ stacks) => tops stacks) . last' . applyCommands commands False $ stacks
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part2 = unwrap . map (\(CR _ _ stacks) => tops stacks) . last' . applyCommands commands True $ stacks
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in do putStrLn "Input: "
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printLn stacks
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putStrLn " "
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putStr "Part 1: "
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putStrLn part1
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putStr "Part 2: "
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putStrLn part2
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Left err => printLn err
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