给一个链表，若其中包含环，请找出该链表的环的入口结点，否则，输出null。
1 # -*- coding:utf-8 -*- 2 # class ListNode: 3 # def __init__(self, x): 4 # self.val = x 5 # self.next = None 6 class Solution: 7 def EntryNodeOfLoop(self, pHead): 8 if pHead == None or pHead.next == None: 9 return None 10 slow = pHead.next 11 fast = pHead.next.next 12 while slow != fast: 13 slow = slow.next 14 fast = fast.next.next 15 fast = pHead 16 while slow != fast: 17 slow = slow.next 18 fast = fast.next 19 return slow 20 # write code here
