# [Add Two Numbers][title]

## Description

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.

**Example**

```
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
```

**Tags:** Linked List, Math


## 思路

题意我也是看了好久才看懂，就是以链表表示一个数，低位在前，高位在后，所以题中的例子就是 `342 + 465 = 807`，所以我们模拟计算即可。

```java
/**
 * 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 node = new ListNode(0);
        ListNode n1 = l1, n2 = l2, t = node;
        int sum = 0;
        while (n1 != null || n2 != null) {
            sum /= 10;
            if (n1 != null) {
                sum += n1.val;
                n1 = n1.next;
            }
            if (n2 != null) {
                sum += n2.val;
                n2 = n2.next;
            }
            t.next = new ListNode(sum % 10);
            t = t.next;
        }
        if (sum / 10 != 0) t.next = new ListNode(1);
        return node.next;
    }
}
```


## 结语

如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-java-leetcode][ajl]



[title]: https://leetcode.com/problems/add-two-numbers
[ajl]: https://github.com/Blankj/awesome-java-leetcode