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  1. import Data.List (sortBy)
  2. import Data.Time (getCurrentTime, diffUTCTime)
  3. import Data.Function (on)
  4.  
  5. data NodeList = NodeList 
  6.     { nlRoot  :: [Int]
  7.     , nlLength :: Int
  8.     , nlSum    :: Int }
  9.     deriving (Show)
  10.  
  11. map1 _ q []    = q
  12. map1 f q (x:xs)  = f x : map1 f q xs
  13.  
  14. makeSums :: [Int] -> Int -> [NodeList] -> [NodeList]
  15. makeSums [] _  acc         = acc    
  16. makeSums (x:xs) maxlen acc = makeSums xs maxlen $ addNodeList $ map1 addNode acc $ filter lessLen acc
  17. 	where addNodeList y = (NodeList [x] 1 x) : y
  18. 	      addNode (NodeList root len sum) = NodeList (x:root) (len+1) (sum+x)
  19. 	      lessLen y = nlLength y < maxlen
  20.  
  21. makePairs :: [NodeList] -> [([Int], [Int])] -> [([Int], [Int])]
  22. makePairs [] acc     = acc
  23. makePairs (x:xs) acc = makePairs xs $ (++) acc $ map pairNodes $ takeWhile sameSum xs 
  24.     where sameSum y = nlSum x == (nlSum y)
  25.           pairNodes y = (nlRoot x, nlRoot y)
  26.  
  27.  
  28. solve :: [Int] -> Int -> [([Int], [Int])]
  29. solve nums maxlen = makePairs (sortBy compareNodes (makeSums nums maxlen [])) []
  30. 	where compareNodes x y = compare (nlSum x) (nlSum y)
  31.  
  32. makePairs1 [] acc     = acc
  33. makePairs1 (x:xs) acc = makePairs1 xs $ map1 pairNodes acc $ takeWhile sameSum xs
  34.     where sameSum y = nlSum x == (nlSum y)
  35.           pairNodes y = (nlRoot x, nlRoot y)
  36.  
  37. solve1 nums maxlen = do
  38. 	let a1 = makeSums nums maxlen []
  39. 	let a2 = sortBy (compare `on` nlSum) a1
  40. 	let a3 = makePairs1 a2 []
  41. 	a3
  42.  
  43. bench f nums maxlen title = do
  44.        begT <- getCurrentTime
  45.        print $ take 1 $ reverse $ f nums maxlen
  46.        endT <- getCurrentTime
  47.        print $ (++) "solve1   " $ show (diffUTCTime endT begT) 
  48.  
  49. test m = bench solve1 [1..m] (m `div` 2) ""   
  50.  
  51. main = test 10 --print $ solve1 [1..4] 3
  52.  
Success #stdin #stdout 0s 4592KB
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Standard input is empty
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[([3],[2,1])]
"solve1   0.002583s"
https://ideone.com/CXhs5M
language:
Haskell (ghc 8.4.4)
created:
10 years ago
visibility:
public

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