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。

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回ListNode12345
    def ReverseList(self, pHead):
	    if pHead == None:
	    	return None
	    if pHead.next == None:
	    	return pHead
	    
	    left = pHead
	    middle = pHead.next
	    right = pHead.next.next
	    # 箭头反指
		left.next = None
		while right:
			# 箭头反指
			middle.next = left
			# 节点向后移动
			left = middle
			middle = right
			right = right.next
		# 最后一个箭头反指
		middle.next = left
		return middle