79 lines
2.5 KiB
Haskell
79 lines
2.5 KiB
Haskell
-- very slow with runghc, use ghc -O3 -o second second.hs
|
|
-- requires cabal install --lib megaparsec parser-combinators
|
|
module Main (main) where
|
|
|
|
import Control.Applicative.Permutations
|
|
import Control.Monad (void, when)
|
|
import Data.Char qualified as C
|
|
import Data.Either
|
|
import Data.List qualified as L
|
|
import Data.Map qualified as M
|
|
import Data.Maybe
|
|
import Data.Set qualified as S
|
|
import Data.Void (Void)
|
|
import Text.Megaparsec
|
|
import Text.Megaparsec.Char
|
|
|
|
exampleExpectedOutput = 467835
|
|
|
|
data Number = Number Int Int Int Int deriving Show -- Value x1 x2 y1
|
|
data Symbol = Symbol Int Int deriving (Eq, Ord, Show) -- x y
|
|
data Input = Input [Number] [Symbol] deriving Show
|
|
|
|
type Parser = Parsec Void String
|
|
|
|
parseNumber :: Parser Number
|
|
parseNumber = do
|
|
(SourcePos _ y' x1') <- getSourcePos
|
|
value <- read <$> some digitChar
|
|
(SourcePos _ _ x2') <- getSourcePos
|
|
let (x1, x2, y) = (unPos x1', unPos x2' - 1, unPos y')
|
|
return $ Number value x1 x2 y
|
|
|
|
parseSymbol :: Parser Symbol
|
|
parseSymbol = do
|
|
(SourcePos _ y' x') <- getSourcePos
|
|
void $ char '*'
|
|
let (x, y) = (unPos x', unPos y')
|
|
return $ Symbol x y
|
|
|
|
parseNumbersAndSymbols :: Parser (Either Number Symbol)
|
|
parseNumbersAndSymbols = do
|
|
many $ void (char '.' <|> symbolChar <|> char '#' <|> char '%' <|> char '@' <|> char '-' <|> char '/' <|> char '&') <|> void eol
|
|
something <- (Left <$> parseNumber) <|> (Right <$> parseSymbol)
|
|
many $ void (char '.') <|> void eol
|
|
return something
|
|
|
|
parseInput' :: Parser Input
|
|
parseInput' = do
|
|
things <- some parseNumbersAndSymbols <* eof
|
|
return $ Input (lefts things) (rights things)
|
|
|
|
parseInput :: String -> IO Input
|
|
parseInput filename = do
|
|
input <- readFile filename
|
|
case runParser parseInput' filename input of
|
|
Left bundle -> error $ errorBundlePretty bundle
|
|
Right input' -> return input'
|
|
|
|
compute :: Input -> Int
|
|
compute (Input nums syms) = sum $ map process syms
|
|
where
|
|
process :: Symbol -> Int
|
|
process sym = case L.foldl' process' [] nums of
|
|
[a, b] -> a * b
|
|
_ -> 0
|
|
where
|
|
process' :: [Int] -> Number -> [Int]
|
|
process' acc (Number v x1 x2 y') | not . S.null $ S.fromList [Symbol x y|x<-[x1-1..x2+1],y<-[y'-1..y'+1]] `S.intersection` S.singleton sym = v:acc
|
|
| otherwise = acc
|
|
|
|
main :: IO ()
|
|
main = do
|
|
example <- parseInput "example"
|
|
print example
|
|
let exampleOutput = compute example
|
|
when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
|
|
input <- parseInput "input"
|
|
print $ compute input
|
|
|