app/cses1068.hs

   1 import Data.List
   2
   3 collatz :: Int -> Int
   4 collatz n | even n = n `div` 2
   5 collatz n | otherwise = 3 * n + 1
   6
   7 collatzStep :: Int -> Maybe (Int, Int)
   8 collatzStep 0 = Nothing
   9 collatzStep 1 = Just (1, 0)
  10 collatzStep n = Just (n, collatz n)
  11
  12 main :: IO ()
  13 main = do
  14   line <- getLine
  15   let n = read line
  16   let nums = unfoldr collatzStep n
  17   let outStr = intercalate " " $ map show nums
  18   putStrLn outStr