You are given the head of a linked list, and an integer k.
Return the head of the linked list after swapping the values of the kth node from the beginning and the kth node from the end (the list is 1-indexed).
Example 1:
Input: head = [1,2,3,4,5], k = 2
Output: [1,4,3,2,5]
Explanation: The 2nd node from the beginning (value 2) and the 2nd node from the end (value 4) are swapped.
Example 2:
Input: head = [7,9,6,6,7,8,3,0,9,5], k = 5
Output: [7,9,6,6,8,7,3,0,9,5]
Explanation: The 5th node from the beginning (value 7) and the 5th node from the end (value 8) are swapped.
Example 3:
Input: head = [1], k = 1
Output: [1]
Explanation: Only one node — nothing to swap.
n1 <= k <= n <= 10⁵0 <= Node.val <= 100