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  1.  
  2.  
  3.  
  4. data DP = Z | L DP | R DP deriving Show
  5.  
  6. ic::DP->Maybe DP
  7. ic Z = Nothing
  8. ic (L n) = Just( R n )
  9. ic (R n) = L <$> (ic n)
  10.  
  11. acc:: DP -> Int
  12. acc Z = 0
  13. acc (L n) = (acc n) + 1
  14. acc (R n) = (acc n) + 1
  15.  
  16. add:: DP -> DP -> Maybe DP
  17.  
  18. add Z _ = Just Z
  19. add _ Z = Just Z
  20.  
  21. add x y
  22.     | ( acc x ) < ( acc y ) = case y of 
  23.         (L z) -> add x z
  24.         (R z) -> add x z
  25.  
  26.     | ( acc x ) < ( acc y ) = case x of 
  27.         (L z) -> add z y
  28.         (R z) -> add z y
  29.  
  30.     | otherwise = case y of 
  31.         (L z) -> case x of 
  32.             (L w) -> L <$> (add z w)
  33.             (R w) -> R <$> (add z w)
  34.             Z -> Nothing 
  35.  
  36.         (R z) -> case (ic x) of 
  37.             Just (L w) -> L <$> (add z w)
  38.             Just (R w) -> R <$> (add z w)
  39.             Nothing -> Nothing
  40.  
  41.  
  42. fromstr :: String -> DP
  43. fromstr ('L' : xs)= L (fromstr xs)
  44. fromstr ('R' : xs)= R (fromstr xs)
  45. fromstr ('Z' : xs)= Z
  46. fromstr (_ : xs)= fromstr xs
  47. fromstr [] = Z
  48.  
  49. main = do {
  50.     x <- (fromstr <$> getLine);
  51.     y <- (fromstr <$> getLine);
  52.     print ( add x y );
  53. }
Success #stdin #stdout 0s 4452KB
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Just (R (L (R Z)))
https://ideone.com/ie13ir
language:
Haskell (ghc 8.4.4)
created:
4 years ago
visibility:
public

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