Add Two Numbers as Linked Lists

You are given two singly linked lists, where each list represents a positive number without any leading zeros.

Your task is to add these two numbers and return the sum as a linked list.

Example:

Input:
The first linked list is 1 -> 2 -> 3 -> 4 -> 5 -> NULL
The second linked list is 4 -> 5 -> NULL
Output:
The linked list representation of the summation is 1 -> 2 -> 3 -> 9 -> 0 -> NULL
Explanation:

The numbers represented are 12345 and 45. The sum is 12390, represented as a linked list 1 -> 2 -> 3 -> 9 -> 0 -> NULL.

Input:

The first line contains an integer 'T', the number of test cases.
Each test case consists of two lines of integers representing the linked list elements, terminated by -1. (-1 is not part of the list elements.)

Output:

For each test case, return the head of the linked list summation. Terminate the linked list elements with -1.

Constraints:

  • 1 <= T <= 100
  • 1 <= L <= 5000 (where L is the number of nodes in either of the linked lists)
  • 0 <= data <= 9 (data is the value of a node, and -1 is not included in list elements)
Note:
You don't need to handle print operations. Just implement the given function.
Follow-Up:
Optimize the solution to achieve linear time and constant space complexity.
AnswerBot
1d

Add two numbers represented as linked lists and return the sum as a linked list.

  • Traverse both linked lists simultaneously while keeping track of carry

  • Create a new linked list to store the sum

  • Handle ca...read more

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