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Top K Frequent Elements

Explore methods to determine the top K most frequent elements in an array by applying heap structures and frequency counting. Understand constraints and implement solutions to solve related coding interview problems effectively.

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Statement

Given an array of integers, arr, and an integer, k, return the kk most frequent elements.

Note: You can return the answer in any order.

Constraints:

  • 11 ≤\leq arr.length ≤\leq 10310^{3}
  • 10−410^{-4} ≤\leq arr[i] ≤\leq 10410^{4}
  • 1 ≤\leq k ≤\leq number of unique elements in an array.
  • It is guaranteed that the answer is unique.

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Top K Frequent Elements

1.

What is the output if the following inputs are given?

arr = [1, 1, 2, 4, 5, 5]

k = 2

A.

[1]

B.

[5]

C.

[1, 5]

D.

[1, 2]

1 / 2

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground:

Java
usercode > FrequentElements.java
import java.util.*;
public class FrequentElements{
    public static List<Integer> topKFrequent(int[] arr, int k) {
        // Replace this placeholder return statement with your code
        return new ArrayList<Integer>();
    }
}
Top K Frequent Elements