advent-of-code/2017/14/day14.hs
2024-11-12 21:46:18 +01:00

41 lines
1.2 KiB
Haskell

#!/usr/bin/env stack
-- stack --resolver lts-9.18 script
import Data.List
import Data.List.Split
import Data.Char
import Data.Bits
import Text.Printf
twist :: [Int] -> Int -> Int -> [Int]
twist xs len skip =
end ++ start
where (knot, keep) = splitAt len xs
(start, end) = splitAt skip $ keep ++ reverse knot
twists :: [Int] -> [Int] -> Int -> [Int]
twists list [] k = list
twists list (x:xs) k = twists (twist list x k) xs (k+1)
hashRound :: Int -> [Int] -> [Int]
hashRound n lens = drop rot list ++ take rot list
where list = foldl' (\acc (x,k) -> twist acc x k) [0..(n-1)] $ zip lens (cycle [0..(n-1)])
rot = n - (sum (zipWith (+) [0..] lens) `rem` n)
sparseHash :: [Int] -> [Int]
sparseHash lengths =
hashRound 256 . concat . replicate 64 $ lengths ++ [17, 31, 73, 47, 23]
denseHash :: [Int] -> [Int]
denseHash h = foldr xor 0 <$> chunksOf 16 h
grid :: String -> [[Int]]
grid input =
map (denseHash . sparseHash . map ord . ((input++"-")++) . show) [0..127]
main :: IO ()
main = do
let input = "stpzcrnm"
let g = grid input
mapM_ (putStrLn . concatMap (printf "%08b")) g
print . length . filter (=='1') . concat $ map (concatMap (printf "%08b")) g