You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

**Input:** (2 -> 4 -> 3) + (5 -> 6 -> 4)

**Output:** 7 -> 0 -> 8

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { // Start typing your Java solution below // DO NOT write main() function ListNode head = new ListNode(-1); ListNode runner = head; int carry = 0; while(l1!=null || l2!=null){ int val1 = l1==null?0:l1.val; int val2 = l2==null?0:l2.val; int sum = val1 + val2 + carry; if(sum>9){ sum = sum - 10; carry = 1; }else{ carry = 0; } if(head.val==-1){ head.val = sum; }else{ ListNode newNode = new ListNode(sum); runner.next = newNode; runner = runner.next; } l1 = l1==null?null:l1.next; l2 = l2==null?null:l2.next; } if(carry==1){ ListNode newNode = new ListNode(1); runner.next = newNode; } return head; } }