LeetCode 2. Add Two Numbers(M)

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.

Python 3:

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

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode,c=0) -> ListNode:
        val=l1.val+l2.val+c
        c=val//10
        rt=ListNode(val%10)
        if(l1.next==None and l2.next==None and c==0):
            return rt
        else:
            if(l1.next==None):
                l1.next=ListNode(0)
            if(l2.next==None):
                l2.next=ListNode(0)
            rt.next=self.addTwoNumbers(l1.next,l2.next,c)
            return rt