力扣-142题（Java）

素颜马尾好姑娘i 2023-01-16 06:54 145阅读 0赞

题目链接：[https://leetcode-cn.com/problems/linked-list-cycle-ii/][https_leetcode-cn.com_problems_linked-list-cycle-ii]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]

/**
     * Definition for singly-linked list.
     * class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) {
     *         val = x;
     *         next = null;
     *     }
     * }
     */
    public class Solution {
        
        public ListNode detectCycle(ListNode head) {
        
            HashSet<ListNode> hash=new HashSet<ListNode>();
            ListNode cur=head;
        
            while(cur!=null){
        
                //在HashSet中没有得到某一个cur的方法，只能直接返回当前的指针
                if(hash.contains(cur)==true) return cur;
                else {
        
                    hash.add(cur);
                    cur=cur.next;
                }
            }
    
            return null;    
        }
    }

[https_leetcode-cn.com_problems_linked-list-cycle-ii]: https://leetcode-cn.com/problems/linked-list-cycle-ii/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20221022/169154d60f9342e0b1bfeb6e8c0f0e7e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]: /images/20221022/5f61aefabc744255b9c89bb95d27d6e8.png