g0301_0400.s0382_linked_list_random_node

Class Solution

java.lang.Object

g0301_0400.s0382_linked_list_random_node.Solution

public class Solution
extends 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 and Description
Solution(ListNode head)

Method Summary

Modifier and Type	Method and Description
int	getRandom()

Methods inherited from class java.lang.Object

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

Constructor Detail

Solution

public Solution(ListNode head)

Method Detail

getRandom

public int getRandom()