作者：CH_Double_C | 来源：互联网 | 2023-12-12 09:09
Givenasinglylinkedlist,returnarandomnode'svaluefromthelinkedlist.Eachnodemusthavethe s
Given a singly linked list, return a random node‘s value from the linked list. Each node must have the same probability of being chosen.
Follow up:
What if the linked list is extremely large and its length is unknown to you? Could you solve this efficiently without using extra space?
Example:
// Init a singly linked list [1,2,3].
ListNode head = new ListNode(1);
head.next = new ListNode(2);
head.next.next = new ListNode(3);
Solution solution = new Solution(head);
// getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning.
solution.getRandom();
1 /**
2 * Definition for singly-linked list.
3 * public class ListNode {
4 * int val;
5 * ListNode next;
6 * ListNode(int x) { val = x; }
7 * }
8 */
9 public class Solution {
10 List list = new ArrayList<>();
11
12 /** @param head The linked list‘s head.
13 Note that the head is guaranteed to be not null, so it contains at least one node. */
14 public Solution(ListNode head) {
15 while (head != null) {
16 list.add(head.val);
17 head = head.next;
18 }
19 }
20
21 /** Returns a random node‘s value. */
22 public int getRandom() {
23 Random rand = new Random();
24 int n = rand.nextInt(list.size());
25 return list.get(n);
26 }
27 }
28
29 /**
30 * Your Solution object will be instantiated and called as such:
31 * Solution obj = new Solution(head);
32 * int param_1 = obj.getRandom();
33 */
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