Lintcode: Add Two Numbers

C++

 /**
  * Definition for singly-linked list.
  * struct ListNode {
  *     int val;
  *     ListNode *next;
  *     ListNode(int x) : val(x), next(NULL) {}
  * };
  */
 class Solution {
 public:
     /**
      * @param l1: the first list
      * @param l2: the second list
      * @return: the sum list of l1 and l2
      */
     ListNode *addLists(ListNode *l1, ListNode *l2) {
         // write your code here
         if (l1 == NULL) {
             return l2;
         }
         if (l2 == NULL) {
             return l1;
         }
         ListNode *ptr1 = l1, *ptr2 = l2;
         ListNode *result = new ListNode(-);
         ListNode *pre = result;
         int carry = , val = ;
         while (ptr1 != NULL || ptr2 != NULL) {
             int val1 = ptr1 == NULL?:ptr1->val;
             int val2 = ptr2 == NULL?:ptr2->val;
             int sum = val1 + val2 + carry;
             val = sum;
             carry = sum/;
             pre->next = new ListNode(val);
             pre = pre->next;
             if (ptr1!=NULL)
             {
                 ptr1 = ptr1->next;
             }
             if (ptr2!=NULL)
             {
                 ptr2 = ptr2->next;
             }
         }
         if (carry == ) {
             pre->next = new ListNode();
         }
         return result->next;
     }
 };