题解 | 链表中环的入口结点

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def EntryNodeOfLoop(self, pHead):
        # write code here
        # 思路是利用map，遇到第一个相同的值说明就是环的入口节点
        mark=[]
        while pHead:
            if pHead.val in mark:
                break
            else:
                mark.append(pHead.val)
                pHead=pHead.next
        return pHead