LeetCode--141--环形链表

问题描述：

给定一个链表，判断链表中是否有环。

思路：用快的指针追慢的指针，只要有圈，一定能追上。

错误:

 class Solution(object):
     def hasCycle(self, head):
         """
         :type head: ListNode
         :rtype: bool
         """
         if head == None or head.next == None:
             return False
         p = head.next
         q = head.next.next
         while p and q:
             if p == q:
                 return True
             p = p.next
             if q.next != None:
                 q = q.next.next
         return False

改正：

 class Solution(object):
     def hasCycle(self, head):
         """
         :type head: ListNode
         :rtype: bool
         """
         if head == None or head.next == None:
             return False
         p = head.next
         q = head.next.next
         while q and q.next:
             if p == q:
                 return True
             p = p.next
             q = q.next.next
         return False

2018-09-12 21:03:17