Posted: 3 Dec, 2020
Difficulty: Easy

## PROBLEM STATEMENT

#### The sum list is a linked list representation of addition of two numbers.

##### Input Format :
``````The first line of input contains a single integer T, representing the number of test cases or queries to be run.

Then the T test cases follow.

The first line of each test case contains the elements of the first singly linked list separated by a single space and terminated by -1. Hence, -1 would never be a list element.

The second line of each test case contains the elements of the second singly linked list separated by a single space and terminated by -1. Hence, -1 would never be a list element.
``````
##### Output Format :
``````For each test case, print the sum linked list. The elements of the sum list should be single-space separated, terminated by -1.

The output of each test case is printed in a separate line.
``````
##### Note :
``````You do not need to print anything, just return the head of the sum linked list.
``````
##### Constraints :
``````1 <= T <= 10
1 <= N <= 5 * 10^4
0 <= data <= 9 and data != -1

Time Limit : 1sec
`````` Approach 1