Given a linked list, determine if it has a cycle in it.<\/p>\n
Follow up:
\nCan you solve it without using extra space?<\/p>\n
Python<\/strong><\/p>\n \r\n# Definition for singly-linked list.\r\nclass ListNode(object):\r\n def __init__(self, x):\r\n self.val = x\r\n self.next = None\r\n\r\nclass Solution(object):\r\n def hasCycle(self, head):\r\n """\r\n :type head: ListNode\r\n :rtype: bool\r\n """\r\n if head is None:\r\n return False\r\n node1 = head\r\n node2 = head\r\n while True:\r\n if node1.next is not None:\r\n node1 = node1.next.next\r\n node2 = node2.next\r\n if node1 is None or node2 is None:\r\n return False\r\n elif node1 == node2:\r\n return True\r\n else:\r\n return False\r\n\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"