[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) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
11         if(l1==null||l2==null)
12             return l1==null?l2:l1;
13         int pre = 0;
14         ListNode newhead=null;
15         ListNode prenode=null;
16         while(l1!=null && l2!=null){
17             int sum = pre + l1.val+ l2.val;
18             ListNode tmp = new ListNode(sum%10);
19             pre=sum/10;
20             if(newhead==null){
21                 newhead=tmp;
22                 prenode=tmp;
23             }else{
24                 prenode.next=tmp;
25                 prenode=tmp;
26             }
27             l1=l1.next;
28             l2=l2.next;
29         }
30         ListNode leftnode= null;
31         if(l1==null)leftnode=l2;
32         else leftnode=l1;
33         while(leftnode!=null){
34             int sum=pre+leftnode.val;
35             ListNode tmp = new ListNode(sum%10);
36             prenode.next=tmp;
37             prenode=tmp;
38             pre=sum/10;
39             leftnode=leftnode.next;
40         }
41         if(pre!=0){
42             ListNode tmp =new ListNode(pre);
43             prenode.next=tmp;
44             tmp.next=null;
45         }
46         return newhead;
47     }
48 }