代码：

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {              ListNode result = null;        ListNode temp = null, node = null;        int digit = 0, bit = 0;        while (l1 != null && l2 != null) {            digit = l1.val + l2.val + bit;            bit = digit / 10;            digit = digit % 10;            node = new ListNode(digit);            if (result == null) {                result = node;                temp = result;            } else {                temp.next = node;                temp = temp.next;            }            l1 = l1.next;            l2 = l2.next;        }        while (l1 != null) {            digit = l1.val + bit;            bit = digit / 10;            digit = digit % 10;            node = new ListNode(digit);            if (result == null) {                result = node;                temp = result;            } else {                temp.next = node;                temp = temp.next;            }            l1 = l1.next;        }        while (l2 != null) {            digit = l2.val + bit;            bit = digit / 10;            digit = digit % 10;            node = new ListNode(digit);            if (result == null) {                result = node;                temp = result;            } else {                temp.next = node;                temp = temp.next;            }            l2 = l2.next;        }        if (bit != 0) {            node = new ListNode(bit);            if (result == null) {                result = node;                temp = result;            } else {                temp.next = node;                temp = temp.next;            }        }        return result;    }}