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.
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]
- 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.