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 } }