Add_two_numbers.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode();
         ListNode temp =dummy;
         int carry =0;
         
         while(l1!=null || l2!=null || carry==1)
         {
             int sum=0;
             if(l1!=null)
             {
                 sum+=l1.val;
                 l1=l1.next;
             }
             if(l2!=null)
             {
                 sum+=l2.val;
                 l2=l2.next;
             }
             
             sum+=carry;
             carry=sum/10;
             ListNode node = new ListNode(sum%10);
             temp.next=node;
             temp=temp.next;
         }
         return dummy.next;
    }
}