2 adding Two Numbers C++/PYTHON

 Description

2. 两数相加 - 力扣（Leetcode）

SOLUTION 

# 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: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        ListHead = ListNode(0)          ##生成一个链表头
        List_ret , cin = ListHead,0     ##定义返回的链表头 和 进标志 cin
        while l1 or l2:                    ##只要不是空的 就继续下去
            sum1 = 0
            if l1:
                sum1 += l1.val
                l1 = l1.next
            if l2:
                sum1 += l2.val
                l2 = l2.next
            if(cin):
                sum1 += cin
            List_ret.next = ListNode(sum1%