I've been solving these challenges in Haskell without using higher order functions.

f (_:x:xs) = x : f xs
f _ = []

The default solution input for Scala is broken. I had to delete the entire object Solution { ... and replace it with def f()...

In Scala:

def f(arr:List[Int]):List[Int] = arr.zipWithIndex.filter(_._2 %2 == 1).map(_._1)

So, zipWithIndex produces pairs like (28,0) (32,1) (5,2) ...

,where the second element is the index and the first the value in the list. Hold only those pairs for which the index is odd(filter), and return the first element of the pair which is the value(map) by applying the function which just describes holding only the first element of the pair.

I ended up with the following haskell solution:

f (x:xs) = (head xs) : f (tail xs)

Obviously, I am a beginner at haskell. Any comments?

f (x:y:ys) = y: (f ys)
f _ = []