2 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

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        if (!l1)
            return l2;
        if (!l2)
            return l1;
        ListNode *dummy = new ListNode(0);
        ListNode *tmp = dummy;
        int carry = 0;
        while(l1 || l2 || carry>0)
        {
            int num1 = l1? l1->val:0;
            int num2 = l2? l2->val:0;
            int sum = (num1+num2+carry)%10;
            carry = (num1+num2+carry)/10;
            tmp->next = new ListNode(sum);
            tmp = tmp->next;
            l1 = l1? l1->next:l1;
            l2 = l2? l2->next:l2;
        }
        tmp = dummy->next;
        delete dummy;
        return tmp;
        
    }
};