leetcode LinkedListRandomNode

import utils.ListNode;
public class LinkedListRandomNode {
  /**
   * 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();
   */
  /** @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 LinkedListRandomNode(ListNode head) {

  }

  /** Returns a random node's value. */
  public int getRandom() {
    return 0;
  }
}