1.题目要求:

2.题目代码:

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
	//设置数组，把链表的结点存入数组中
    vector<int> array;
    Solution(ListNode* head) {
        ListNode* cur = head;
        while(cur){
            array.push_back(cur->val);
            cur = cur->next;
        }
		//设置随机种子
        srand((unsigned)time(NULL));
    }
    
    int getRandom() {
       //控制随机范围
        int randomindex = rand() % array.size();
        return array[randomindex];
    }
};

/**
 * Your Solution object will be instantiated and called as such:
 * Solution* obj = new Solution(head);
 * int param_1 = obj->getRandom();
 */