Reverse Linked List in Groups

Given a singly linked list, reverse the nodes of the list k at a time and return the modified list. If the number of nodes is not a multiple of k, leave the last nodes as is. You must do this in-place and use only constant extra space. Input format: - The first line contains an integer n, the number of nodes in the list. - The second line contains n integers, the node values of the list. - The third line contains an integer k, the group size for reversal. Output format: - Print the transformed list as space-separated integers in order. Example: Input: 5 1 2 3 4 5 2 Output: 2 1 4 3 5