Reverse Linked List in Groups of K

You are provided with a linked list containing 'N' nodes and an integer 'K'. The task is to reverse the linked list in groups of size K, which means reversing the nodes in each group (1,K),(K+1,2*K), etc.

Example:

Input:

List: [1, 2, 3, 4, 5, 6], K = 2

Output:

[2, 1, 4, 3, 6, 5]

Explanation:

The nodes are reversed in pairs: [1, 2] -> [2, 1], [3, 4] -> [4, 3], [5, 6] -> [6, 5].

Constraints:

• 1 <= T <= 100
• 1 <= N <= 10^4
• 1 <= K <= 10^4
• Time Limit: 1sec

Input:

The first line of input contains an integer 'T' representing the number of test cases. Each test case follows with:
1. A line containing a linked list where elements are separated by spaces and the list is terminated by -1.
2. A line containing the integer K.

Output:

For each test case, output the modified linked list elements, separated by spaces, on a new line.

Note:

• If the number of elements in the last group cannot be evenly divided by K, reverse that last group. For example, for list [1, 2, 3, 4, 5] and K = 3, the output is [3, 2, 1, 5, 4].
• All node values in the linked list are distinct.