danger.hs.txt

Ulm大学2003-2004年竞赛题

-- Problem   In Danger
-- Algorithm Recursion
-- Runtime   O(log(n))
-- Author    Walter Guttmann
-- Date      06.05.2001

main :: IO ()
main =
  do input <- readFile "danger.in"
     mapM_ (print . solve) $ takeWhile (> 0) $ map (round . read) $ words input

solve :: Int -> Int
solve n | n == 1         = 1
        | n `mod` 2 == 1 = solve ((n-1) `div` 2) * 2 + 1
        | otherwise      = solve (n `div` 2) * 2 - 1