2 Add Two Numbers(easy)

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

给定两个非空的链表，表示两个非负整数。 数字以相反的顺序存储，每个节点包含一个数字。 添加两个数字并将其作为链表返回。

您可以假设两个数字不包含任何前导零，除了数字0本身。

思考：以一个变量记录两个链表对应的元素和的十位，便利两个链表

while (l1 != null || l2 != null || carry != 0) {
ListNode cur = new ListNode(0);
int sum = ((l2 == null) ? 0 : l2.val) + ((l1 == null) ? 0 : l1.val) + carry;
cur.val = sum % 10;
carry = sum / 10;
prev.next = cur;
prev = cur;
l1 = (l1 == null) ? l1 : l1.next;
l2 = (l2 == null) ? l2 : l2.next;
}