【LeetCode with Python】 Linked List Cycle

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原题页面：https://oj.leetcode.com/problems/linked-list-cycle/

题目类型：

难度评价：★

本文地址：/article/1377542.html

Given a linked list, determine if it has a cycle in it.

Follow up:

Can you solve it without using extra space?

确定链表是否有环。记得好像是编程之美上的题目？

class Solution:
    # @param head, a ListNode
    # @return a boolean
    def hasCycle(self, head):
        if None == head:
            return False
        fast = slow = head
        while True:
            fast = fast.next
            if None == fast:
                return False
            fast = fast.next
            if None == fast:
                return False
            slow = slow.next
            if fast == slow:
                return True