NOWCODER 剑指offer 反转链表

运行时间：28ms

占用内存：5624k

三个变量，pre，current，cnext

以及注意最后的返回值是pre，因为current已经移出链表为null，而pre保留了前一个current的值

# -*- 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
        pre = None
        current = pHead
        #cnext = None
        #temp = None
        while(current):
            cnext = current.next
            current.next = pre
            pre = current
            current = cnext
        return pre