Package g0301_0400.s0382_linked_list_random_node

Class Solution

java.lang.Object
g0301_0400.s0382_linked_list_random_node.Solution
public class Solution extends java.lang.Object
382 - Linked List Random Node.

Medium

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.

Implement the Solution class:

  • Solution(ListNode head) Initializes the object with the integer array nums.
  • int getRandom() Chooses a node randomly from the list and returns its value. All the nodes of the list should be equally likely to be choosen.

Example 1:

Input

 ["Solution", "getRandom", "getRandom", "getRandom", "getRandom", "getRandom"] 
 [[[1, 2, 3]], [], [], [], [], []]

Output:

 [null, 1, 3, 2, 2, 3]

Explanation:

 Solution solution = new Solution([1, 2, 3]); 
 solution.getRandom(); // return 1 
 solution.getRandom(); // return 3 
 solution.getRandom(); // return 2 
 solution.getRandom(); // return 2 
 solution.getRandom(); // return 3 
 // getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning.

Constraints:

  • The number of nodes in the linked list will be in the range [1, 104].
  • -104 <= Node.val <= 104
  • At most 104 calls will be made to getRandom.

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?

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution(ListNode head)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    getRandom()
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution(ListNode head)

  • Method Details

    • getRandom

      public int getRandom()