Add Two Numbers

AddTwoNumbers.Java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class AddTwoNumbers {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode iterator1 = l1;
        ListNode iterator2 = l2;
        ListNode solution = new ListNode(-1);
        ListNode solutionIterator = solution;
        int carry = 0;
        int sum = 0;
        while(iterator1 != null || iterator2 != null) {
            sum += carry;
            if(iterator1 != null) {
                sum += iterator1.val;
                iterator1 = iterator1.next;
            }
            if(iterator2 != null) {
                sum += iterator2.val;
                iterator2 = iterator2.next;
            }
            if(solutionIterator.val >= 0) {
                solutionIterator.next = new ListNode(-1);
                solutionIterator = solutionIterator.next;
            }
            solutionIterator.val = sum % 10;
            carry = sum / 10;
            sum = 0;
        }
        if(carry > 0) {
            solutionIterator.next = new ListNode(carry);
        }
        return solution;
    }
}