牛客网 反转列表

# -*- 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 not pHead or not pHead.next:
            return pHead
        last=None
        
        while pHead:
            tmp=pHead.next
            pHead.next=last
            last=pHead
            pHead=tmp
        return last