【LeetCode】141.环形链表

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# @Time: 2019/3/26
# @Author: xfLi
# The file...


class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

def hasCycle(head):
    cur = head
    res = set()
    while cur:
        if cur in res:
            return True
        else:
            res.add(cur)
            cur = cur.next
    return False