链表加法。

解答1[Java]：

核心思想

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummyHead = new ListNode(0);
        ListNode p1 = l1;
        ListNode p2 = l2;
        ListNode result = dummyHead;
        int carry = 0;
        int sum;

        while (p1 != null || p2 != null) {
            int x = (p1 != null) ? p1.val : 0;
            int y = (p2 != null) ? p2.val : 0;
            sum = x + y + carry;
            carry = sum / 10;
            result.next = new ListNode(sum % 10);
            result = result.next;
            if (p1 != null) {
                p1 = p1.next;
            }
            if (p2 != null) {
                p2 = p2.next;
            }
        }
        if (carry > 0) {
            result.next = new ListNode(carry);
        }

        return dummyHead.next;
    }
}

进阶：链表中的数是正向存储的

思路1：给较短链表的长度和较长链表的长度补齐，补的高位节点的值都设为0。