Add Two Numbers

The problem 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. Examples Input: l1 = [2,4,3], l2 = [5,6,4] Output: [7,0,8] Explanation: 342 + 465 = 807. Input: l1 = [0], l2 = [0] Output: [0] Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9] Output: [8,9,9,9,0,0,0,1] 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. Explanation When we add two numbers, we need to remember the carry value when it’s necessary. The main caveat in this problem is the edge cases; we will discuss them later. From the description of the problem, we know that we are given two non‑empty linked lists without negative integers, and the digits are stored in reverse order; we will see later that this reverse order will help us solve the problem. ...