Given a singly linked list of size N, and an integer K. You need to swap the K^th node from beginning and Kth node from the end in the linked list.
Note: You need to swap the nodes through the links and not changing the content of the nodes.

Example 1:

Input:
N = 4,  K = 1
value[] = {1,2,3,4}
Output: 1
Explanation: Here K = 1, hence after
swapping the 1st node from the beginning
and end thenew list will be 4 2 3 1.

Example 2:

Input:
N = 5,  K = 3
value[] = {1,2,3,4,5}
Output: 1
Explanation: Here k = 3, hence after
swapping the 3rd node from the beginning
and end the new list will be 1 2 3 4 5.

Your Task: 
The task is to complete the function swapkthnode(), which has arguments head, num(no of nodes), and K, and it should return a new head. The validation is done internally by the driver code to ensure that the swapping is done by changing references/pointers only.  A correct code would always cause output as 1.

Expected Time Complexity: O(n)
Expected Auxillary space Complexity: O(1)

Constraints:
1 <= N <= 10³
1 <= K <= 10³