Ninety-Nine Haskell Problems: Problem 2

one xs = xs !! (length xs - 2)

two xs = reverse xs !! 1

three = aux
  where
    aux [x,y] = x
    aux (x:xs) = aux xs

four xs = aux xs (length xs)
  where
    aux xs 2 = head xs
    aux (x:xs) l = aux xs (l - 1)

five xs = snd . head . filter (\(x, _) -> x == 1) $ zip (reverse xs) [0 ..]

six = head . tail . reverse

seven = last . init