leetcode 链表 两数相加

 两数相加

 

 

给定两个非空链表来表示两个非负整数。位数按照逆序方式存储，它们的每个节点只存储单个数字。将两数相加返回一个新的链表。

你可以假设除了数字 0 之外，这两个数字都不会以零开头。

示例：

输入：(2 -> 4 -> 3) + (5 -> 6 -> 4)
输出：7 -> 0 -> 8
原因：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, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        head = ListNode(0)
        cur = head
        m = 0
        while True:
            if l1 is not None:
                a = l1.val
            else:
                a = 0
            if l2 is not None:
                b = l2.val
            else:
                b = 0
            if l1 is None and l2 is None and m == 0:
                return head.next
            else:
                add = a + b + m
                cur.next = ListNode(add % 10)
                m = (a+b+m) // 10
                cur = cur.next
            if l1 is not None:
                l1 = l1.next
            if l2 is not None:
                l2 = l2.next