haskell házi 1

rotate1.hs

rotate :: String -> [String]
rotate l = rotate_recursive l []

rotate_recursive :: String -> String -> [String]
rotate_recursive [] list = []
rotate_recursive list1 list2 =
	let (h1:t1) = list1
	in [list1 ++ list2] ++ rotate_recursive t1 (list2 ++ [h1])

-- http://code.google.com/codejam/contest/1460488/dashboard#s=p2

is_recycled :: String -> String -> Bool
is_recycled l1 l2 = length [ x | x <- rotate l1, x /= l1, x == l2] >= 1

recycled_numbers :: Int -> Int -> Int
recycled_numbers from to = length [ (x,y) |
	x <- [from..to], y <- [from..to], x < y, is_recycled (show x) (show y) ]