题解 | #判断链表中是否有环#

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

    return false;

}