Add Two Numbers(Leetcode002)

''' 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. 给出两个非空的链表用来表示两个非负的整数。 其中它们各自的位数是按照 逆序 的方式存储的，并且它们的每个节点只能存储一位数字。 如果我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。 您可以假设除了数字 0 之外，这两个数都不会以 0 开头。 Example: Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807. ''' # 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: res = ListNode(0) r = res carry = 0 while l1 or l2: x = l1.val if l1 else 0 y = l2.val if l2 else 0 s = carry + x + y carry = s // 10 r.next = ListNode(s % 10) r = r.next if l1 is not None: l1 = l1.next if l2 is not None: l2 = l2.next if carry > 0: r.next = ListNode(1) return res.next