leetcode

 1 struct ListNode {
 2    int val;
 3     ListNode *next;
 4     ListNode(int x) : val(x), next(NULL) {}
 5 };
 6 
 7 class Solution {
 8 public:
 9     ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
10 
11         if (l1 == NULL)
12             return l2;
13         if (l2 == NULL)
14             return l1;
15 
16         unsigned long int v1 = -1, v2 = -1, v3 = 0;
17 
18         ListNode *p1 = l1, *p2 = l2, *l3 = NULL, *p3 = l3;
19         ListNode *pt = NULL;
20         int count = 0;
21         while (p1){
22             if ( count==0 )
23                 v1 = p1->val;
24             else{
25                 int temp=1;
26                 for (int i = 1; i <= count; i++)
27                     temp = 10 * temp;
28 
29                 v1 = temp* (p1->val) + v1;
30             }
31 
32             count++;
33             p1 = p1->next;
34         }
35 
36         count = 0;
37         while (p2){
38             if (count == 0)
39                 v2 = p2->val;
40             else{
41                 int temp = 1;
42                 for (int i = 1; i <= count; i++)
43                     temp = 10 * temp;
44 
45                 v2 = temp* (p2->val) + v2;
46             }
47 
48             count++;
49             p2 = p2->next;
50         }
51 
52         v3 = v1 + v2;
53 
54         while (v3 / 10 != 0){
55             pt = new ListNode(v3 % 10);
56             if (l3 == NULL){
57                 pt->next = NULL;
58                 l3 = pt;
59             }
60             else{
61                 pt->next = p3->next;
62                 p3->next = pt;
63                 p3 = pt;
64             }
65             v3 = v3 / 10;
66             p3 = pt;
67         }
68         if (v3 != 0){
69             pt = new ListNode(v3);
70             pt->next = p3->next;
71             p3->next = pt;
72             p3 = pt;
73         }
74 
75         p3->next = NULL;
76 
77         return l3;
78     }
79 };