[LeetCode] Add Two Numbers, Solution

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

» Solve this problem

[Thoughts]
Similar as "Add Binary". The only difference is the pointer operation.


[Code]

1:    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {  
2:            ListNode* result = new ListNode(-1);  
3:            ListNode* pre = result;  
4:            ListNode *pa = l1, *pb = l2;  
5:            int carry =0;  
6:            while(pa!=NULL || pb!=NULL)  
7:            {  
8:                 int av = pa == NULL? 0:pa->val;  
9:                 int bv = pb == NULL? 0:pb->val;  
10:                 ListNode* node = new ListNode((av+bv+carry)%10);  
11:                 carry = (av+bv+carry)/10;  
12:                 pre->next = node;  
13:                 pre = pre->next;  
14:                 pa = pa==NULL? NULL:pa->next;  
15:                 pb = pb==NULL? NULL:pb->next;  
16:            }            
17:            if(carry >0)  
18:                 pre->next = new ListNode(1);  
19:            pre = result->next;  
20:            delete result;  
21:            return pre;  
22:       }