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

public ListNode addTwoNumbers(ListNode l1, ListNode l2) { // Start typing your Java solution below // DO NOT write main() function ListNode runner1=l1; ListNode runner2=l2; ListNode head = new ListNode(-1); ListNode runner = head; int carry=0; while(runner1!=null || runner2!=null ||carry!=0){ int val1 = runner1==null?0:runner1.val; int val2 = runner2==null?0:runner2.val; int sum =val1+val2+carry; if(sum>9){ carry=1; }else{ carry=0; } runner.next = new ListNode(sum%10); runner = runner.next; runner1 = runner1==null?null:runner1.next; runner2 = runner2==null?null:runner2.next; } return head.next; }