LeetCode-Linked_List_Cycle
经典的链表题，判断一个链表是否存在循环，而且不许使用额外的空间，解题思路：只要分别设定一个快慢指针，当快慢指针重合时就证明有循环，原题链接：https://leetcode.com/problems/linked-list-cycle/
Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
# _*_ coding: utf-8 _*_
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def hasCycle(self, head):
"""
:type head: ListNode
:rtype: bool
判断一个链表是不是存在循环
"""
if not head:
return False
slow = fast = head
while fast and fast.next:
slow, fast = slow.next, fast.next.next
if fast == slow:
return True
return False