打卡群刷题总结0615——两数相加

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        res = ListNode(0)
        node = res
        add = 0
        node1, node2 = l1, l2

        while node1 or node2:
            # node1不为空
            if node1:
                add += node1.val
                node1 = node1.next
            # node2不为空
            if node2:
                add += node2.val
                node2 = node2.next
            # 链表元素 & 进位
            node.next = ListNode(add % 10)
            add //= 10
            node = node.next

        # 最后一个进位
        if add:
            node.next = ListNode(1)

        return res.next