题目：

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

思路：

就像做加法一样，记得进位和判断结尾

package list;public class AddTwoNumbers {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode p = new ListNode(0);        ListNode node = p;        int sum = 0;        int carry = 0;        while (true) {            if (l1 != null && l2 != null) {                sum = l1.val + l2.val + carry;                l1 = l1.next;                l2 = l2.next;            } else if (l1 != null) {                sum = l1.val + carry;                l1 = l1.next;            } else if (l2 != null){                sum = l2.val + carry;                l2 = l2.next;            } else {                sum = carry;                if (sum == 0)                    break;            }                        p.next = new ListNode(sum % 10);            carry = sum / 10;            p = p.next;        }                return node.next;    }        public static void main(String[] args) {        // TODO Auto-generated method stub    }}