LinkedLists - Add two numbers

AddTwoNumbers.java

package com.interviewbytes.linkedlists;


class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}

public class AddTwoNumbers {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        int carry = 0;

        ListNode sentinel = new ListNode(0);

        ListNode current = sentinel;

        while (l1 != null || l2 != null) {
            int a = 0;
            int b = 0;

            if (l1 != null) {
                a = l1.val;
                l1 = l1.next;
            }

            if (l2 != null) {
                b = l2.val;
                l2 = l2.next;
            }

            int sum = a + b + carry;
            current.next = new ListNode(sum % 10);
            current = current.next;
            carry = sum / 10;
        }

        if (carry > 0) current.next = new ListNode(carry);

        return sentinel.next;
    }
}