Reverse Alternate K Nodes Problem Statement

You are given a singly linked list of integers along with a positive integer 'K'. The task is to modify the linked list by reversing every alternate 'K' nodes of the linked list.

Explanation:

A singly linked list is a type of linked list that allows traversal in only one direction from the head to the tail node.

Input:

The input consists of multiple test cases. For each test case, the first line contains elements of the singly linked list separated by a space, ending with -1. Note -1 is not a list element.
The second line contains the positive integer 'K'.

Output:

For each test case, return the modified linked list by reversing every alternate K nodes. The output should be space-separated elements terminated by -1.

Example:

Input: 
Linked list: 5 6 7 8 9 10 11 12 
K: 3 

Output:
7 6 5 8 9 10 12 11 -1

Explanation:
Reverse the first 'K' (3) nodes, then skip the next 'K' (3) nodes. Since only 2 nodes are left, which is less than 'K', reverse them. The resulting list is: 7 6 5 8 9 10 12 11.

• Constraints:
• 1 ≤ T ≤ 10
• 1 ≤ N ≤ 5 * 104
• 1 ≤ K ≤ N
• -103 ≤ data ≤ 103, with data ≠ -1

Note: Implement the given function. Printing is handled automatically.