Solution: Reverse Nodes in k-Group

Statement

The task is to reverse the nodes in groups of $k$ in a given linked list, where $k$ is a positive integer, and at most the length of the linked list. If any remaining nodes are not part of a group of $k$, they should remain in their original order.

It is not allowed to change the values of the nodes in the linked list. Only the order of the nodes can be modified.

Note: Use only $O(1)$ extra memory space.

Constraints:

Let n be the number of nodes in a linked list.

• $1 \leq$ k $\leq$ n $\leq 500$