Leetcode 2. Add Two Numbers(java版)

题目：

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.

题目大意：

给两个连个链表，链表中储存着两个逆序的数字，你要将两个数字相加，并将结果逆序放入链表返回。

example：

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

思路：

因为链表中数字逆序，结果也要逆序，所以可以直接逆序相加，注意进位。

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) {        if(l1 == null&&l2 == null) {            return null;        }        ListNode temp = new ListNode(0);        ListNode ans = temp;        int value1 = 0;        int value2 = 0;        while(l1 != null&&l2 != null)        {            value1 = (l1.val + l2.val + value2) % 10;            value2 = (l1.val + l2.val + value2) / 10;            temp.next = new ListNode(value1);            l1 = l1.next;            l2 = l2.next;            temp = temp.next;            if(l1 == null&&l2 == null)                break;            if(l1 == null)                l1 = new ListNode(0);            if(l2 == null)                l2 = new ListNode(0);        }        if(value2 != 0)            temp.next = new ListNode(value2);        return ans.next;    }}