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

代码：

 1     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
 2         // IMPORTANT: Please reset any member data you declared, as
 3         // the same Solution instance will be reused for each test case.
 4         if(l1 == NULL)
 5             return l2;
 6         if(l2 == NULL)
 7             return l1;
 8         ListNode *result, *tmp;
 9         int carry = 0;
10         tmp = new ListNode(0);
11         result = tmp;
12         while(l1 && l2){
13             tmp->next = new ListNode(0);
14             tmp->next->val = l1->val + l2->val + carry;
15             carry = tmp->next->val/10;
16             tmp->next->val = tmp->next->val%10;
17             tmp = tmp->next;
18             l1 = l1->next;
19             l2 = l2->next;
20         }
21         if(l1 == NULL)
22             tmp->next = l2;
23         else
24             tmp->next = l1;
25         while(carry == 1){
26             if(tmp->next == NULL)
27                 tmp->next = new ListNode(0);
28             tmp->next->val++;
29             carry = tmp->next->val/10;
30             tmp->next->val = tmp->next->val%10;
31             tmp = tmp->next;
32         }
33         return result->next;
34     }