add two num

# coding:utf-8# 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.##Definition for singly-linked list.class ListNode(object):    def __init__(self, x):        self.val = x        self.next = Noneclass Solution(object):    def addTwoNumbers(self, l1, l2):        """        :type l1: ListNode        :type l2: ListNode        :rtype: ListNode        """        addition = cur = ListNode(0)        carry = 0        if carry or l1 or l2:            if l1:                carry = carry + l1.val                l1 = l1.next            if l2:                carry = carry + l2.val                l2 = l2.next            cur.next = ListNode(carry%10)            cur = cur.next            carry //=10        return addition.next