【Leetcode】Linked List Cycle

Given a linked list, determine if it has a cycle in it.

Follow up:

Can you solve it without using extra space?

这个问题也比较简单，我就直接贴出解题部分的代码了~

问题的核心在于设一个快指针和一个慢指针，如果“有一天”慢的追上了快的，说明中间一定有环儿~

Public class LLCycle {/** * Definition for singly-linked list. * class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */class ListNode{int val;ListNode next;ListNode(int x){val = x;next=null;}}<span style="white-space:pre"></span>//以下为解题部分    public boolean hasCycle(ListNode head) {    if(head==null||head.next==null)return true;    ListNode slow=head;    ListNode fast=head;        while(true){                if(fast==null||fast.next==null)return true;        slow=slow.next;        fast=fast.next.next;        if(fast==slow)return false;                        }    }}