コラッツ列とか #CodePiece

CodePiece.hs

quicksort :: (Ord a) => [a] -> [a]
quicksort [] = []
quicksort (x:xs) =
  let smallOrEqual = filter (<= x) xs
      larger = filter (> x) xs
  in quicksort smallOrEqual ++ [x] ++ quicksort larger

largestDivisible :: [Int] -> Bool
largestDivisible [] = False
largestDivisible (x:xs)
  | (x `mod` 3829) == 0 = True
  | otherwise = largestDivisible xs

largest2829 :: Integer
largest2829 = head (filter p [100000,99999..])
  where p x = (x `mod` 2829) == 0

chain :: Integer -> [Integer]
chain 1 = [1]
chain n
  | even n = n : chain (n `div` 2)
  | odd n  = n : chain (n * 3 + 1)

calcChain :: Int
calcChain = length (filter isLong (map chain [1..100]))
  where isLong x = length x > 15