# [2. 两数相加](https://leetcode-cn.com/problems/add-two-numbers)

[English Version](/solution/0000-0099/0002.Add%20Two%20Numbers/README_EN.md)

## 题目描述

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<p>给出两个&nbsp;<strong>非空</strong> 的链表用来表示两个非负的整数。其中，它们各自的位数是按照&nbsp;<strong>逆序</strong>&nbsp;的方式存储的，并且它们的每个节点只能存储&nbsp;<strong>一位</strong>&nbsp;数字。</p>

<p>如果，我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。</p>

<p>您可以假设除了数字 0 之外，这两个数都不会以 0&nbsp;开头。</p>

<p><strong>示例：</strong></p>

<pre><strong>输入：</strong>(2 -&gt; 4 -&gt; 3) + (5 -&gt; 6 -&gt; 4)
<strong>输出：</strong>7 -&gt; 0 -&gt; 8
<strong>原因：</strong>342 + 465 = 807
</pre>

## 解法

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### **Python3**

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```python
# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        carry = 0
        dummy = ListNode(-1)
        cur = dummy
        while l1 or l2 or carry:
            t = (0 if not l1 else l1.val) + (0 if not l2 else l2.val) + carry
            carry = t // 10
            cur.next = ListNode(t % 10)
            cur = cur.next
            l1 = None if not l1 else l1.next
            l2 = None if not l2 else l2.next
        return dummy.next
```

### **Java**

<!-- 这里可写当前语言的特殊实现逻辑 -->

```java
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int carry = 0;
        ListNode dummy = new ListNode(-1);
        ListNode cur = dummy;
        while (l1 != null || l2 != null || carry != 0) {
            int t = (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val) + carry;
            carry = t / 10;
            cur.next = new ListNode(t % 10);
            cur = cur.next;
            l1 = l1 == null ? null : l1.next;
            l2 = l2 == null ? null : l2.next;
        }
        return dummy.next;
    }
}
```

### **C#**

```cs
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode AddTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(-1);
        ListNode cur = dummy;
        var carry = 0;
        while (l1 != null || l2 != null || carry != 0)
        {
            int t = (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val) + carry;
            carry = t / 10;
            cur.next = new ListNode(t % 10);
            cur = cur.next;
            l1 = l1 == null ? null : l1.next;
            l2 = l2 == null ? null : l2.next;
        }
        return dummy.next;
    }
}
```

### **...**

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```

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