Reversing Linked List
Given a constant?K?and a singly linked list?L, you are supposed to reverse the links of every?K?elements on?L. For example, given?Lbeing 1→2→3→4→5→6, if?K=3, then you must output 3→2→1→6→5→4; if?K=4, you must output 4→3→2→1→5→6.