Reverse Doubly Linked List Nodes in Groups

You are given a doubly linked list of integers along with a positive integer K that represents the group size. Your task is to modify the linked list by reversing every group of K nodes. If the number of nodes left in the list or the last group is fewer than K, reverse those remaining nodes as well.

Input:

First line: Integer T, the number of test cases.
For each test case: 
 - First line: Elements of the doubly linked list separated by a single space, ending with -1 (indicating the end of the list; -1 is not a list element). 
 - Second line: Integer K.

Output:

For each test case, print the modified linked list with the elements separated by a single space, ending with -1.

Example:

Input:

Linked list: 8 9 10 11 12 K: 3

Output:

10 9 8 12 11 -1

Explanation:

Reverse the first 3 nodes, resulting in 10, 9, 8. The remaining 2 nodes (11 and 12) are fewer than 3, so they are reversed to 12, 11.

Constraints:

• 1 ≤ T ≤ 10
• 1 ≤ N ≤ 5 × 104
• 1 ≤ K ≤ 105
• -103 ≤ data ≤ 103 and data ≠ -1
• Time Limit: 1 sec