leetcode-2.两数相加
题目描述
给你两个 非空 的链表,表示两个非负的整数。它们每位数字都是按照 逆序 的方式存储的,并且每个节点只能存储 一位 数字。
请你将两个数相加,并以相同形式返回一个表示和的链表。
你可以假设除了数字 0 之外,这两个数都不会以 0 开头。
示例 1:
输入:l1 = [2,4,3], l2 = [5,6,4] 输出:[7,0,8] 解释:342 + 465 = 807.
示例 2:
输入:l1 = [0], l2 = [0] 输出:[0]
示例 3:
输入:l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9] 输出:[8,9,9,9,0,0,0,1]
思路
1. 循环的条件:l1,l2,进位,至少还有一个有值,就循环下去
2. 链表节点的值由3部分组成:l1.val+l2.val+进位
2.1 节点的值:3个数的和 % 10
2.2 进位:3个数的和 // 10
3. l1,l2,头节点各自next
# Definition for singly-linked list.
class ListNode(object):def __init__(self, val=0, next=None):self.val = valself.next = next
class Solution(object):def addTwoNumbers(self, l1, l2):""":type l1: ListNode:type l2: ListNode:rtype: ListNode"""head = pre = ListNode(-1)val = carry = 0while l1 or l2 or carry > 0:val = carryif l1:val += l1.vall1 = l1.nextif l2:val += l2.vall2 = l2.nextcarry = val // 10head.next = ListNode(val % 10)head = head.nextreturn pre.nextif __name__=='__main__':s=Solution()head1=ListNode(9)phead1=head1data1=[9,9,9,9,9,9]for i in data1:node=ListNode(i)phead1.next=nodephead1=phead1.nexthead2 = ListNode(9)phead2 = head2data2 = [9,9,9]for i in data2:node = ListNode(i)phead2.next = nodephead2 = phead2.nexthead = s.addTwoNumbers(head1,head2)while head:print(head.val)head=head.next