C Program to swap kth node from first and kth node from last in a Linked List

Consider you have the following linked list and you want to swap second node from first and second node from last .

The steps are given below .

     1)Get the size of the linked list . If the size is less than k you can't swap the element . And in the above linked list if k value is 3 you dont need to swap the element .
     2)The two pointers kthnodefromfirst and kthnodefromlast used to point the nodes that we need to swap and its previous nodes are pointed using previous1,previous2.
     3)swap the two nodes . And while swapping you need to check whether you are swapping the head or not . Its one of the important test case .

Code:(in C)

Time Complexity : O(n)
Space Complexity: O(1)

Please let me know if you have any questions .