This problem was asked by Airbnb.
Given a linked list and a positive integer k, rotate the list to the right by k places.
For example, given the linked list 7 -> 7 -> 3 -> 5 and k = 2, it should become 3 -> 5 -> 7 -> 7.
Given the linked list 1 -> 2 -> 3 -> 4 -> 5 and k = 3, it should become 3 -> 4 -> 5 -> 1 -> 2.