原题链接：

2. 两数相加
https://leetcode.cn/problems/add-two-numbers/

完成情况：

解题思路：

	 * 主要关注两个点：*      1.ListNode对齐，位数少的，补0*      2.考虑进位

参考代码：

package 西湖算法题解___中等题;public class __2两数相加 {// Definition for singly-linked list.public class ListNode {int val;ListNode next;ListNode() {}ListNode(int val) { this.val = val; }ListNode(int val, ListNode next) { this.val = val; this.next = next; }}public static void main(String[] args) {}public ListNode addTwoNumbers(ListNode l1, ListNode l2) {/*** 主要关注两个点：*      1.ListNode对齐，位数少的，补0*      2.考虑进位*/ListNode pre = new ListNode(0);ListNode cur = pre;int need_addBit = 0;while (l1 != null || l2 != null){int x = l1 == null? 0:l1.val;int y = l2 == null? 0:l2.val;int sum = x+y+need_addBit;need_addBit = sum/10;   //判断是否要进位sum%=10;    //保留过10的余数cur.next = new ListNode(sum);cur = cur.next;if (l1 != null){l1 = l1.next;}if (l2 != null){l2 = l2.next;}if (need_addBit == 1){cur.next = new ListNode(need_addBit);}}return pre.next;}//public ListNode addTwoNumbers(ListNode l1, ListNode l2)}