Add Two Numbers

 //by anniekim

    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        ListNode dummy(0), *cur = &dummy;
        int carry = 0;
        while (l1 || l2 || carry){
            int sum = carry;
            if (l1) {
            sum += l1->val;
            l1 = l1->next;
            }
            if (l2) {
            sum += l2->val;
            l2 = l2->next;
            }
            carry = sum >= 10 ? 1 : 0;
            sum %= 10;
            ListNode *newNode = new ListNode(sum);
            cur->next = newNode;
            cur = newNode;
        }
        return dummy.next;
    }