61. Rotate List 
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Problem
Given the head of a linked list, rotate the list to the right by k places.
Example 1:
Input: head = [1,2,3,4,5], k = 2 Output: [4,5,1,2,3]
Example 2:
Input: head = [0,1,2], k = 4 Output: [2,0,1]
Constraints:
- The number of nodes in the list is in the range
[0, 500]. -100 <= Node.val <= 1000 <= k <= 2 * 109