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authorJulien Dessaux2024-12-21 01:16:43 +0100
committerJulien Dessaux2024-12-21 01:16:43 +0100
commit46beea085f7f0c6ac6cb36cc37bf149701cf4be0 (patch)
treefbb815e9f89578235b5acd721ac3a917028b3997 /2024/17-Chronospatial_Computer/second.hs
parent2024-16 in haskell (diff)
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2024-17 in haskell
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+-- 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