/*

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

*/

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

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

* }

*/

public class Solution {

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

ListNode pre = new ListNode(0);

ListNode head = pre;

int carry = 0;

while(l1 != null || l2 != null || carry != 0){

ListNode cur = new ListNode(0);//这里cur必须放在while循环里，每次重新定义一个新的cur

int sum = ((l1==null) ? 0 : l1.val) + ((l2 == null) ? 0 : l2.val) + carry;

cur.val = sum % 10;

carry = sum / 10;

pre.next = cur;

pre = cur;

l1 = (l1 == null) ? l1:l1.next;

l2 = (l2 == null) ? l2:l2.next;

}

return head.next;

}

}