Add Two Numbers Represented by Linked Lists

Your task is to find the sum list of two numbers represented by linked lists and return the head of the sum list.

Explanation:

The sum list should be a linked list representation of the addition of the two numbers.

Input:

The first line of input contains a single integer T, indicating the number of test cases to be processed.

For each test case, there are two lines of input:
- The first line contains the elements of the first linked list, separated by spaces and ending with -1. The -1 is not part of the list elements.
- The second line contains the elements of the second linked list, also separated by spaces and ending with -1.

Output:

For each test case, print the sum linked list with elements separated by spaces and ending with -1.
Each test case should have its output on a new line.

Example:

Input:
2
7 5 9 4 6 -1
8 4 -1
5 6 3 -1
8 4 2 -1

Output:
5 0 0 5 0 -1
1 4 0 6 -1

Constraints:

• 1 ≤ T ≤ 10
• 1 ≤ N ≤ 5 * 10⁴
• 0 ≤ data ≤ 9 and data ≠ -1

Note:

You are not required to print anything; return the head of the sum linked list.