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
10 void addtolist(int val, int& add, ListNode*&head, ListNode*&pre)
11 {
12 int sum = val + add;
13 if (sum >= 10){
14 add = 1;
15 sum -= 10;
16
17 }
18 else {
19 add = 0;
20 }
21 ListNode *node = new ListNode(sum);
22 if (!head){
23 head = node;
24 }
25 if (NULL != pre) {
26 pre->next = node;
27 }
28 pre = node;
29 }
30
31 class Solution {
32 public:
33 ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
34 if (!l1 && !l2){
35 return NULL;
36 }
37 ListNode *head = NULL;
38 ListNode *pre = NULL;
39 int add = 0;
40 while (l1 != NULL && l2 != NULL){
41 addtolist(l1->val + l2->val, add, head, pre);
42 l1 = l1->next;
43 l2 = l2->next;
44 }
45 while (l1){
46 addtolist(l1->val, add, head, pre);
47 l1 = l1->next;
48 }
49 while (l2){
50 addtolist(l2->val, add, head, pre);
51 l2 = l2->next;
52 }
53 if (add){
54 addtolist(0, add, head, pre);
55 }
56 return head;
57 }
58 };
