leetCode算法题目之我解（2)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

需要注意的是进位和指针操作！

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1. /**
   
2.  * Definition for singly-linked list.
   
3.  * struct ListNode {
   
4.  * int val;
   
5.  * ListNode *next;
   
6.  * ListNode(int x) : val(x), next(NULL) {}
   
7.  * };
   
8.  */
   
9. class Solution {
   
10. public:
    
11.     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
    
12.     ListNode *result = l1;
    
13.     ListNode *p1 = l1;
    
14.     ListNode *p2 = l2;
    
15.     ListNode *pre = l1;
    
16.     int s = 0;
    
17.     while (p1 && p2) {
    
18.         pre = p1;
    
19.         int temp = s;
    
20.         s = (p1->val + p2->val + s) / 10;
    
21.         p1->val = (p1->val + p2->val + temp) % 10;
    
22.         p1 = p1->next;
    
23.         p2 = p2->next;
    
24.     }
    
25.     if (p2) {
    
26.      pre->next = p2;
    
27.         p1 = p2;
    
28.     }
    
29.     while (p1) {
    
30.         pre = p1;
    
31.         if (s != 0) {
    
32.             int temp = s;
    
33.             s = (p1->val + s) / 10;
    
34.             p1->val = (p1->val + temp) % 10;
    
35.             p1 = p1->next;
    
36.         } else {
    
37.             break;
    
38.         }
    
39.     }
    
40.     if (s) {
    
41.         pre->next = new ListNode(s);
    
42.     }
    
43.     return result;
    
44.     }
    
45. };