javal链表相加求和！

面试遇到一算法题：

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

琢磨了一阵子，希望可以帮到有缘人。代码如下：

  public class ListNode {    int val;    ListNode next;    ListNode(int x) { val = x; }} public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode  listNode= new ListNode(0);        ListNode p = new ListNode(0);        p = listNode;        int sum = 0;        while (l1 != null || l2 != null || sum != 0) {            if (l1 != null) {                sum += l1.val;                l1 = l1.next;            }            if (l2 != null) {                sum += l2.val;                l2 = l2.next;            }            p.next = new ListNode(sum % 10);            sum = sum / 10;            p = p.next;        }        return listNode.next;    }}