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  1. subsequencesOfSize :: Int -> [a] -> [[a]]
  2. subsequencesOfSize n xs | n > length xs = []
  3. subsequencesOfSize n xs = subsequencesBySize xs !! n where
  4. 	subsequencesBySize    []  = [[[]]]
  5. 	subsequencesBySize (x:xs) = zipWith (++) ([] : map (map (x:)) next) (next ++ [[]])
  6. 		where next = subsequencesBySize xs
  7.  
  8. main = do
  9. 	print $ length $ subsequencesOfSize 3   [1..350]
  10. 	print $ length $ subsequencesOfSize 147 [1..150]
Success #stdin #stdout 2.2s 9336KB
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7084700
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https://ideone.com/LrpZMh
language:
Haskell (ghc 8.4.4)
created:
9 years ago
visibility:
secret

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