77 lines
2.7 KiB
Haskell
77 lines
2.7 KiB
Haskell
|
-- requires cabal install --lib megaparsec parser-combinators heap vector
|
||
|
module Main (main) where
|
||
|
|
||
|
import Control.Monad (void, when)
|
||
|
import Data.Bits
|
||
|
import Data.Functor
|
||
|
import qualified Data.List as L
|
||
|
import Data.Maybe
|
||
|
import Data.Void (Void)
|
||
|
import Text.Megaparsec
|
||
|
import Text.Megaparsec.Char
|
||
|
|
||
|
type Register = Int
|
||
|
type Op = Int
|
||
|
data Input = Input [Register] [Op] deriving Show
|
||
|
|
||
|
type Parser = Parsec Void String
|
||
|
|
||
|
parseNumber :: Parser Int
|
||
|
parseNumber = read <$> some digitChar
|
||
|
|
||
|
parseRegister :: Parser Register
|
||
|
parseRegister = string "Register " *> (char 'A' <|> char 'B' <|> char 'C') *> string ": " *> parseNumber
|
||
|
|
||
|
parseInput' :: Parser Input
|
||
|
parseInput' = Input <$> some (parseRegister <* eol) <* eol
|
||
|
<*> (string "Program: " *> some (parseNumber <* optional (char ',')) <* eol <* eof)
|
||
|
|
||
|
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'
|
||
|
|
||
|
type Pointer = Int
|
||
|
type PState = (Pointer, [Register], [Int])
|
||
|
|
||
|
compute :: Input -> Int
|
||
|
compute (Input start ops) = minimum $ findA 0 (tail $ L.reverse $ L.tails ops)
|
||
|
where
|
||
|
findA :: Int -> [[Int]] -> [Int]
|
||
|
findA a [] = [a]
|
||
|
findA a (l:ls) = concatMap (\next -> findA next ls) nexts
|
||
|
where
|
||
|
candidates :: [Int]
|
||
|
candidates = [a*8..a*8+7]
|
||
|
steps :: [PState]
|
||
|
steps = map (\x -> step (0, [x, 0, 0], [])) candidates
|
||
|
outputs :: [[Int]]
|
||
|
outputs = map (\(_, [_, _, _], x') -> reverse x') steps
|
||
|
valids :: [Int]
|
||
|
valids = L.elemIndices l outputs
|
||
|
nexts :: [Int]
|
||
|
nexts = map (candidates L.!!) valids
|
||
|
end = length ops
|
||
|
step :: PState -> PState
|
||
|
step ps@(p, [a, b, c], _) | p == end = ps
|
||
|
| otherwise = step $ i ps co
|
||
|
where
|
||
|
i = [adv, bxl, bst, jnz, bxc, out, bdv, cdv] L.!! (ops L.!! p)
|
||
|
co = [0, 1, 2, 3, a, b, c] L.!! (ops L.!! (p+1))
|
||
|
adv (p, [a, b, c], acc) n = (p+2, [a `div` (2 ^ n), b, c], acc)
|
||
|
bxl (p, [a, b, c], acc) n = (p+2, [a, xor b n, c], acc)
|
||
|
bst (p, [a, b, c], acc) n = (p+2, [a, n `mod` 8, c], acc)
|
||
|
jnz (p, [0, b, c], acc) n = (p+2, [0, b, c], acc)
|
||
|
jnz (p, [a, b, c], acc) n = (n, [a, b, c], acc)
|
||
|
bxc (p, [a, b, c], acc) _ = (p+2, [a, xor b c, c], acc)
|
||
|
out (p, [a, b, c], acc) n = (p+2, [a, b, c], (n `mod` 8) : acc)
|
||
|
bdv (p, [a, b, c], acc) n = (p+2, [a, a `div` (2 ^ n), c], acc)
|
||
|
cdv (p, [a, b, c], acc) n = (p+2, [a, b, a `div` (2 ^ n)], acc)
|
||
|
|
||
|
main :: IO ()
|
||
|
main = do
|
||
|
input <- parseInput "input"
|
||
|
print $ compute input
|