【LeetCode】Add Two Numbers

/**
 * 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) {
        ListNode *head = new ListNode(0);
	ListNode *ptr;
	ptr = head;
	int val1, val2;
	int carry = 0;
	while (l1 || l2)
	{
		val1 = 0;
		if (l1)
		{
			val1 = l1->val;
			l1 = l1->next;
		}
		val2 = 0;
		if (l2)
		{
			val2 = l2->val;
			l2 = l2->next;
		}
		int num = val1 + val2 + carry;
		carry = num / 10;
		ptr->next = new ListNode(num % 10);
		ptr = ptr->next;
		
	}
	if(carry>0)
	{
	    ptr->next=new ListNode(carry);
	}
	return head->next;
    }
};