# Add Two Numbers(linked list)

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.
```

分析

while l1 or l2 or carry:包含所有情况，记得cur l1 l2都要往下走

```
# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        carry = 0
        dummy = ret = ListNode(-1)
        while l1 or l2 or carry:
            if l1:
                carry += l1.val
                l1 = l1.next
            if l2:
                carry += l2.val
                l2 = l2.next
            ret.next = ListNode(carry%10)
            ret = ret.next
            carry //= 10 

        return dummy.next
```


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