链表相加

# 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) -> ListNode:
        p=ListNode(0)
        m=p
        carry=0
        sum1=0
        while carry>0 or l1 or l2:
            val1=l1.val if l1 else 0
            val2=l2.val if l2 else 0
            sum1=val1+val2+carry
            carry=sum1//10
            val=sum1%10
            m.next=ListNode(val)
            if l1:
                l1=l1.next
            if l2:
                l2=l2.next
            m=m.next
        return p.next