第七周 12.23-12.29（链表）

1.链表两数相加（2）

# 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:
        re = ListNode(0)
        r = re
        c = 0
        while(l1 or l2):#遍历两个链表
            x = l1.val if l1 else 0
            y = l2.val if l2 else 0
            s = c + x + y
            c = s//10  #取进位
            r.next = ListNode(s%10)
            r = r.next
            if (l1!=None):l1 = l1.next
            if (l2!=None):l2 = l2.next
        if (c>0):
            r.next = ListNode(1)
        return re.next