I created a function for riffle that works fine, but I don't know how to approach part b.

In HASKELL,

a) Using recursion, define a function riffle :: [a] -> [a] -> [a] that takes two lists of the same length, and interleaves their elements. For example, riffle [1,2,3] [4,5,6] = [1,4,2,5,3,6].

b) Define a function shuffle :: Int -> [a] -> [a] that takes a natural number n and an even-lengthed list, and splits and then riffles the list n times. For example, shuffle 2 [1,2,3,4,5,6] = [1,5,4,3,2,6].