LeetCode: Add Two Numbers 题解

 1 class Solution {
 2 public:
 3     ListNode *add(ListNode *l1, ListNode *l2,int c)
 4     {
 5         ListNode *head= new ListNode(0);
 6         if(l1==NULL && l2==NULL)
 7         {
 8             if(c==0)
 9                return NULL;
10             else
11             {
12                 head->val=1;
13                return head;
14             }
15         }
16         if(l1==NULL)
17             return add(head,l2,c);
18         if(l2==NULL)
19             return add(l1,head,c);
20 
21         if(l1!=NULL && l2!=NULL)
22         {
23            head->val =(l1->val + l2->val +c)%10;
24            c = (l1->val + l2->val +c)/10;
25            head->next = add(l1->next,l2->next,c);
26         }
27         return head;
28     }
29     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
30         int c=0;
31         if(l1==NULL) return l2;
32         if(l2==NULL) return l1;
33 
34         ListNode *head = add(l1,l2,c);
35         return head;
36     }
37 };