117 lines
4 KiB
Haskell
117 lines
4 KiB
Haskell
-- requires cabal install --lib megaparsec parser-combinators heap vector
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module Main (main) where
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import Control.Applicative.Permutations
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import Control.Monad (void, when)
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import qualified Data.Char as C
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import Data.Either
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import Data.Functor
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import qualified Data.Heap as H
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import qualified Data.List as L
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import qualified Data.Map as M
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import Data.Maybe
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import qualified Data.Set as S
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import qualified Data.Vector as V
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import qualified Data.Vector.Unboxed as VU
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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import Debug.Trace
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exampleExpectedOutput = 19114
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data Category = X | M | A | S deriving (Eq, Show)
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data Op = Gt | Lt deriving (Eq, Show)
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data Action = Accept | Reject | Jmp String deriving (Eq, Show)
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data Rule = Cmp Category Op Int Action | RuleAction Action deriving (Eq, Show)
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type Workflow = (String, [Rule])
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type Workflows = M.Map String [Rule]
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data Part = Part Int Int Int Int deriving (Eq, Show)
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type Parts = [Part]
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data Input = Input Workflows Parts deriving (Eq, Show)
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type Parser = Parsec Void String
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parseCategory :: Parser Category
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parseCategory = char 'x' $> X
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<|> char 'm' $> M
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<|> char 'a' $> A
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<|> char 's' $> S
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parseOp :: Parser Op
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parseOp = char '>' $> Gt
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<|> char '<' $> Lt
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parseNumber :: Parser Int
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parseNumber = read <$> some digitChar
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parseLabel :: Parser String
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parseLabel = try $ count' 2 4 letterChar
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parseAction :: Parser Action
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parseAction = char 'A' $> Accept
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<|> char 'R' $> Reject
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<|> (Jmp <$> parseLabel)
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parseRule :: Parser Rule
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parseRule = (RuleAction <$> parseAction)
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<|> (Cmp <$> parseCategory <*> parseOp <*> parseNumber <* char ':' <*> parseAction)
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parseWorkflow :: Parser Workflow
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parseWorkflow = (,) <$> parseLabel <* char '{'
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<*> some (parseRule <* optional (char ',')) <* char '}'
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parseWorkflows :: Parser Workflows
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parseWorkflows = M.fromList <$> some (parseWorkflow <* eol)
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parsePart :: Parser Part
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parsePart = Part <$> (string "{x=" *> parseNumber)
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<*> (string ",m=" *> parseNumber)
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<*> (string ",a=" *> parseNumber)
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<*> (string ",s=" *> parseNumber <* char '}')
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parseParts :: Parser Parts
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parseParts = some (parsePart <* eol)
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parseInput' :: Parser Input
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parseInput' = Input <$> (parseWorkflows <* eol)
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<*> (parseParts <* eof)
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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compute :: Input -> Int
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compute (Input workflows parts) = sum $ map compute' parts
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where
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compute' :: Part -> Int
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compute' (Part x m a s) = case evaluate entryPoint of
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Accept -> x + m + a + s
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Reject -> 0
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where
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evaluate :: [Rule] -> Action
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evaluate (RuleAction (Jmp s):_) = evaluate $ workflows M.! s
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evaluate (RuleAction a:_) = a
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evaluate (Cmp cat op n r:xs) | matches cat op n x m a s = evaluate [RuleAction r]
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| otherwise = evaluate xs
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matches X Lt n x _ _ _ = x < n
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matches X Gt n x _ _ _ = x > n
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matches M Lt n _ m _ _ = m < n
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matches M Gt n _ m _ _ = m > n
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matches A Lt n _ _ a _ = a < n
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matches A Gt n _ _ a _ = a > n
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matches S Lt n _ _ _ s = s < n
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matches S Gt n _ _ _ s = s > n
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entryPoint = workflows M.! "in"
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main :: IO ()
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main = do
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example <- parseInput "example"
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let exampleOutput = compute example
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when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
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input <- parseInput "input"
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print $ compute input
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