Linked List Cycle

目录

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

Follow up:
Can you solve it without using extra space?

两个node,速度不同,循环
slow 为 慢
fast为快

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/**
* 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) {
ListNode slow = head;
ListNode fast = head;
while(fast!=null&&fast.next!=null){
slow=slow.next;
fast=fast.next.next;
if(slow==fast){
return true;
}
}
return false;
}
}