141. 环形链表

﹏ヽ暗。殇╰゛Y 2023-02-12 13:27 23阅读 0赞

# 题目： #

[141. 环形链表][141.]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70]

# 题解： #

## 1. 题解一：利用set求解 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][20200526122715504.gif]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 2]

## 2. 题解二：双指针（快慢指针） ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 4]

# 代码： #

## 1. 代码一：利用set求解 ##

// 方法1：
    public static boolean hasCycle(ListNode head) { 
        Set<ListNode> set = new HashSet<>(); // 哈希表去重
        boolean flag = false;
        while(head != null)
        { 
            if(set.contains(head))
            { 
                flag = true;
                break;
            }
            set.add(head);
            head = head.next;
        }
        return flag;  
    }

## 2. 代码二：双指针（快慢指针） ##

// 方法2：
    public static boolean hasCycle(ListNode head) { 
        if(head == null || head.next == null)
        { 
            return false;
        }
        ListNode fast = head;
        ListNode slow = head;
        boolean flag = false;
        while(fast != null && fast.next != null)
        { 
            fast = fast.next.next;
            slow = slow.next;
            if(fast == slow)
            { 
                flag = true;
                break;
            }
        }
        return flag;
    }

# 参考： #

1.  [环形链表][Link 1]
2.  [链表有环最佳解答][Link 2]
3.  [动画演示 141. 环形链表][141. 1]

[141.]: https://leetcode-cn.com/problems/linked-list-cycle/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200526122427197.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200526122628671.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[20200526122715504.gif]: https://img-blog.csdnimg.cn/20200526122715504.gif
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200526122926932.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/2020061522324288.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20200526123157864.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[Link 1]: https://leetcode-cn.com/problems/linked-list-cycle/solution/huan-xing-lian-biao-by-leetcode/
[Link 2]: https://leetcode-cn.com/problems/linked-list-cycle/solution/lian-biao-you-huan-zui-jia-jie-da-by-tinet-shenjg/
[141. 1]: https://leetcode-cn.com/problems/linked-list-cycle/solution/dong-hua-yan-shi-141-huan-xing-lian-biao-by-user74/