Leetcode 141. Linked List Cyclejava language

Given A linked list, determine if it has a cycle in it. Follow Up:can you solve it without using extra space?

Test instructions: Judging the chain list has no ring

/** * 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)  {         ///defines two fast and slow pointers. If you have a ring, the fast pointer will meet the slow pointer. Otherwise, the quick pointer will advance to the tail         ////should be my that will of the entrance examination of the topic ca         if (head==null | |  head.next==null | |  head.next.next==null) return false;        listnode  Fast=head.next.next;        listnode slow=head.next;         while (Fast!=slow) {            if ( Fast.next!=null && fast.next.next!=null) {                 fast=fast.next.next;                 slow=slow.next;                 }else{                 //fast early to the end of                  return false;             }                     }        return true;    }} 

PS: Fast and Slow pointer. Pay attention to judging boundary conditions

Leetcode 141. Linked List Cyclejava language