Leetcode-Add Two Numbers

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
14         if (l1==null) return l2;
15         if (l2==null) return l1;
16 
17         ListNode preHead = new ListNode(0);
18         ListNode end = preHead;
19         int carry = 0;
20         while (l1!=null || l2!=null){
21             int val = carry;
22             if (l1!=null) val += l1.val;
23             if (l2!=null) val += l2.val;            
24             carry = val/10;
25             val = val%10;
26             ListNode newNode = new ListNode(val);
27             end.next = newNode;
28             end = newNode;
29             if (l1!=null) l1 = l1.next;
30             if (l2!=null) l2 = l2.next;
31         }
32         if (carry!=0){
33             ListNode newNode = new ListNode(carry);
34             end.next = newNode;
35         }
36 
37 
38         return preHead.next;
39         
40     }
41 }