Write a program to reverse every K elements of a linked list.
Example: K = 3
1->2->3->4->5->6->NULL
output: 3->2->1->6->5->4-NULL
Write a program to reverse every K elements of a linked list.
Example: K = 3
1->2->3->4->5->6->NULL
output: 3->2->1->6->5->4-NULL