【leetcode】 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

class Solution {
public:
    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        int carry = 0;
        ListNode *l3 = new ListNode(0);
        ListNode *p3 = l3;
        while(l1 !=NULL || l2!= NULL){
            if(l1 != NULL){
                carry += l1->val;
                l1 = l1->next;
            }
            if(l2 != NULL){
                carry += l2->val;
                l2 = l2->next;
            }

            l3->next = new ListNode(carry % 10);
            carry = carry/10;
            l3 = l3->next;
        }
        if(carry == 1)
            l3->next = new ListNode(1);
        return p3->next;
    }
};