leetcode 382. Linked List Random Node | 382. 链表随机节点（Java）

Bertha 。 2022-08-31 06:56 146阅读 0赞

## 题目 ##

[https://leetcode.com/problems/linked-list-random-node/][https_leetcode.com_problems_linked-list-random-node]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

先存起来，再随机返回即可。不知道在考察什么？

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */
    class Solution { 
        List<Integer> list;
        java.util.Random rand = new java.util.Random();
    
        /** @param head The linked list's head. Note that the head is guaranteed to be not null, so it contains at least one node. */
        public Solution(ListNode head) { 
            list = new LinkedList<>();
            while (head != null) { 
                list.add(head.val);
                head = head.next;
            }
        }
    
        /** Returns a random node's value. */
        public int getRandom() { 
            return list.get(rand.nextInt(list.size()));
        }
    }
    /** * Your Solution object will be instantiated and called as such: * Solution obj = new Solution(head); * int param_1 = obj.getRandom(); */

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode.com_problems_linked-list-random-node]: https://leetcode.com/problems/linked-list-random-node/submissions/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20220829/799b114fb35b46a79276c7d270f48fe3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20220829/e424081d403243c29d2f34d3d2ef83ed.png