Package g0301_0400.s0381_insert_delete_getrandom_o1_duplicates_allowed

Class RandomizedCollection

java.lang.Object

g0301_0400.s0381_insert_delete_getrandom_o1_duplicates_allowed.RandomizedCollection

public class RandomizedCollection
extends Object

381 - Insert Delete GetRandom O(1) - Duplicates allowed.<p>Hard</p> <p><code>RandomizedCollection</code> is a data structure that contains a collection of numbers, possibly duplicates (i.e., a multiset). It should support inserting and removing specific elements and also removing a random element.</p> <p>Implement the <code>RandomizedCollection</code> class:</p> <ul> <li><code>RandomizedCollection()</code> Initializes the empty <code>RandomizedCollection</code> object.</li> <li><code>bool insert(int val)</code> Inserts an item <code>val</code> into the multiset, even if the item is already present. Returns <code>true</code> if the item is not present, <code>false</code> otherwise.</li> <li><code>bool remove(int val)</code> Removes an item <code>val</code> from the multiset if present. Returns <code>true</code> if the item is present, <code>false</code> otherwise. Note that if <code>val</code> has multiple occurrences in the multiset, we only remove one of them.</li> <li><code>int getRandom()</code> Returns a random element from the current multiset of elements. The probability of each element being returned is <strong>linearly related</strong> to the number of same values the multiset contains.</li> </ul> <p>You must implement the functions of the class such that each function works on <strong>average</strong> <code>O(1)</code> time complexity.</p> <p><strong>Note:</strong> The test cases are generated such that <code>getRandom</code> will only be called if there is <strong>at least one</strong> item in the <code>RandomizedCollection</code>.</p> <p><strong>Example 1:</strong></p> <p><strong>Input</strong></p> <pre><code> [&quot;RandomizedCollection&quot;, &quot;insert&quot;, &quot;insert&quot;, &quot;insert&quot;, &quot;getRandom&quot;, &quot;remove&quot;, &quot;getRandom&quot;] [ [], [1], [1], [2], [], [1], []] </code></pre> <p><strong>Output:</strong> [null, true, false, true, 2, true, 1]</p> <p><strong>Explanation:</strong></p> <pre><code> RandomizedCollection randomizedCollection = new RandomizedCollection(); randomizedCollection.insert(1); // return true since the collection does not contain 1. // Inserts 1 into the collection. randomizedCollection.insert(1); // return false since the collection contains 1. // Inserts another 1 into the collection. Collection now contains [1,1]. randomizedCollection.insert(2); // return true since the collection does not contain 2. // Inserts 2 into the collection. Collection now contains [1,1,2]. randomizedCollection.getRandom(); // getRandom should: // - return 1 with probability 2/3, or // - return 2 with probability 1/3. randomizedCollection.remove(1); // return true since the collection contains 1. // Removes 1 from the collection. Collection now contains [1,2]. randomizedCollection.getRandom(); // getRandom should return 1 or 2, both equally likely. </code></pre> <p><strong>Constraints:</strong></p> <ul> <li><code>-2³¹ <= val <= 2³¹ - 1</code></li> <li>At most <code>2 * 10⁵</code> calls <strong>in total</strong> will be made to <code>insert</code>, <code>remove</code>, and <code>getRandom</code>.</li> <li>There will be <strong>at least one</strong> element in the data structure when <code>getRandom</code> is called.</li> </ul>

Constructor Summary

Constructors

Constructor	Description
RandomizedCollection()

Method Summary

Modifier and Type	Method	Description
int	getRandom()
boolean	insert(int val)
boolean	remove(int val)

Methods inherited from class java.lang.Object

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

Constructor Details

RandomizedCollection

public RandomizedCollection()

Method Details

insert

public boolean insert(int val)

remove

public boolean remove(int val)

getRandom

public int getRandom()