Add Two Numbers

来源：Leetcode

原帖：http://oj.leetcode.com/problems/add-two-numbers/

题目：
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：

 /**  
  * Definition for singly-linked list.  
  * struct ListNode {  
  *   int val;  
  *   ListNode *next;  
  *   ListNode(int x) : val(x), next(NULL) {}  
  * };  
  */  
 class Solution {  
 public:  
     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {  
         ListNode dummy(0);  
         ListNode *cur = &dummy;  
         int carry = 0;  
         while (l1 || l2 || carry) {  
             int sum = carry;  
             if (l1) {  
                 sum += l1->val;  
                 l1 = l1->next;  
             }  
             if (l2) {  
                 sum += l2->val;  
                 l2 = l2->next;  
             }  
             carry = sum / 10;  
             sum %= 10;  
             cur->next = new ListNode(sum);  
             cur = cur->next;  
         }  
         return dummy.next;  
     }  
 };