2. Add Two Numbers

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

Solution:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int sum = 0; 
        ListNode rts=new ListNode(0);
        ListNode r = rts;
        while(l1!=null||l2!=null){
            sum /= 10;
            if(l1!=null){
                sum += l1.val;
                l1=l1.next;
            }
            if(l2!=null){
                sum += l2.val;
                l2= l2.next;
            }
            ListNode temp = new ListNode(sum%10);
            rts.next = temp;
            rts = rts.next;

        }

        if(sum/10 == 1){
            rts.next = new ListNode(1);
        }

        return r.next;
    }
}