剑指offer——反转链表

题目描述

输入一个链表，反转链表后，输出新链表的表头。

使用语言：python

1：递归方法

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回ListNode
    def ReverseList(self, pHead):
        # write code here
        if pHead==None or pHead.next==None:
            return pHead
        newphead= self.ReverseList(pHead.next)
        pHead.next.next=pHead
        pHead.next=None
        return newphead

　　

 

非递归方法：

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回ListNode
    def ReverseList(self, pHead):
        # write code here
        if pHead==None or pHead.next==None:
            return pHead

        last= None
        while(pHead):
            tmp=pHead.next
            pHead.next=last
            last=pHead
            pHead=tmp
        return last

　　

偷个懒：图示详解可参考https://blog.csdn.net/FX677588/article/details/72357389。