DIY: Reverse Nodes in k-Group

Solve the interview question "Reverse Nodes in k-Group", in this lesson.

Problem statement

Given a linked list, you will reverse the nodes of the linked list k at a time and return the modified list.

k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k, then the nodes left in the end ...