app/cses2205.hs

   1 import Data.Word
   2 import Data.Bits
   3 import Numeric (showIntAtBase)
   4 import Data.Char (intToDigit)
   5
   6 main :: IO ()
   7 main = do
   8   line1 <- getLine
   9   let nBits = read line1 :: Int
  10   let n = fromIntegral $ 2 ^ nBits
  11   let codes = [toGray x | x <- [0..(n - 1)]]
  12   putStrLn $ unlines $ map (showBits nBits) codes
  13
  14 toGray :: Word16 -> Word16
  15 toGray n = n `xor` (n `shiftR` 1)
  16
  17 showBits :: Int -> Word16 -> String
  18 showBits k n = prefix ++ suffix
  19   where suffix = showIntAtBase 2 intToDigit n ""
  20         prefix = replicate (k - length suffix) '0'