Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
给定一个链表，检测内部是否有cycle
算法分析
方法一
通过哈希表来解决问题
Java代码
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public boolean hasCycle(ListNode head) {
Set<ListNode> listSet = new HashSet<>();
while(head != null) {
if (listSet.contains(head))
return true;
else
listSet.add(head);
head = head.next;
}
return false;
}
}
