牛客网 剑指Offer JZ15 反转链表

描述

输入一个链表，反转链表后，输出新链表的表头。

 

输入{1,2,3}

输出{3,2,1}

 

class Solution:

    def ReverseList(self, pHead):
        if pHead is None or pHead.next is None:
            return pHead
        pnext = None
        pre = None
        
        while(pHead is not None):
            pnext = pHead.next
            pHead.next = pre
            pre = pHead
            pHead = pnext
        return pre