数据结构之环形链表

  public boolean hasCycle(ListNode head) {
        if (head == null || head.next == null)return false;
        ListNode lowNode = head;//使用快慢指针的方法
        ListNode fastNode = head.next.next;
        while(fastNode != null && fastNode.next != null){
            if (lowNode == fastNode){//如果有环,慢指针就会就会追上快指针
                return true;
            }else{
                lowNode = lowNode.next;
                fastNode = fastNode.next.next;
            }
        }
        
        return false;
    }

https://leetcode-cn.com/problems/linked-list-cycle/submissions/