LeetCode: 2.Add Two Numbers

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
11         ListNode c1 = l1;
12         ListNode c2 = l2;
13         ListNode sentinel = new ListNode(0);
14         ListNode d = sentinel;
15         int sum = 0;
16         //当两个链表的next均不为null时
17         while (c1 != null || c2 != null) {
18             //将进位累加到下一个元素和
19             sum /= 10;
20             if (c1 != null) {
21                 sum += c1.val;
22                 c1 = c1.next;
23             }
24             if (c2 != null) {
25                 sum += c2.val;
26                 c2 = c2.next;
27             }
28             //只保留个位上的数
29             d.next = new ListNode(sum % 10);
30             d = d.next;
31         }
32         //如果最后一对元素之和大于10，将进位1直接给下一个节点
33         if (sum / 10 == 1)
34             d.next = new ListNode(1);
35         return sentinel.next;
36     }
37 }