Challenge Statement
- You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.
- You may assume the two numbers do not contain any leading zero, except the number 0 itself.
- This challenge corresponds to LeetCode #2.
Constraints
- The number of nodes in each linked list is in the range
[1, 100]. 0 <= Node.val <= 9- It is guaranteed that the list represents a number that does not have leading zeros.
Example 1:
Input: l1 = [2, 4, 3], l2 = [5, 6, 4]
Output: [7, 0, 8]
Explanation: 342 + 465 = 807
Example 2:
Input: l1 = [0], l2 = [0]
Output: [0]
Example 3:
Input: l1 = [9, 9, 9, 9, 9, 9, 9], l2 = [9, 9, 9, 9]
Output: [8, 9, 9, 9, 0, 0, 0, 1]
Solution
Below is my solution and some test cases. This solution has a linear time complexity O(n) and a constant space complexity O(1), where n is the length of the input list.