Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
题意：
给定一个链表，判断是否有环
思路：
快慢指针
若有环，则快慢指针一定会在某个节点相遇(此处省略证明)
代码：
1 public class Solution { 2 public boolean hasCycle(ListNode head) { 3 ListNode fast = head; 4 ListNode slow = head; 5 while(fast != null && fast.next != null){ 6 fast = fast.next.next; 7 slow = slow.next; 8 if(fast == slow) return true; 9 } 10 return false; 11 } 12 }
[leetcode]141. Linked List Cycle判断链表是否有环
原文：https://www.cnblogs.com/liuliu5151/p/9227172.html