Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
# 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
"""
slow = head
fast = head
while fast != None and fast.next != None:
fast = fast.next.next
slow = slow.next
if fast == slow:
return True
return False
