Java Dequeue | HackerRank Programming Solutions | HackerRank Java Solutions

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JAVA was developed by James Gosling at Sun Microsystems Inc in the year 1991, later acquired by Oracle Corporation. It is a simple programming language. Java makes writing, compiling, and debugging programming easy. It helps to create reusable code and modular programs.

Java is a class-based, object-oriented programming language and is designed to have as few implementation dependencies as possible. A general-purpose programming language made for developers to write once run anywhere that is compiled Java code can run on all platforms that support Java. Java applications are compiled to byte code that can run on any Java Virtual Machine. The syntax of Java is similar to c/c++.

Link for the ProblemJava Dequeue – Hacker Rank Solution

Java Dequeue – Hacker Rank Solution

Problem :

In computer science, a double-ended queue (dequeue, often abbreviated to deque, pronounced deck) is an abstract data type that generalizes a queue, for which elements can be added to or removed from either the front (head) or back (tail).

Deque interfaces can be implemented using various types of collections such as LinkedList or ArrayDeque classes. For example, deque can be declared as:

Deque deque = new LinkedList<>();
Deque deque = new ArrayDeque<>();

You can find more details about Deque here.

In this problem, you are given  integers. You need to find the maximum number of unique integers among all the possible contiguous subarrays of size .

Note: Time limit is  second for this problem.

Input Format

The first line of input contains two integers  and : representing the total number of integers and the size of the subarray, respectively. The next line contains  space separated integers.


The numbers in the array will range between .

Output Format

Print the maximum number of unique integers among all possible contiguous subarrays of size .

Sample Input

6 3
5 3 5 2 3 2

Sample Output

Java Dequeue – Hacker Rank Solution
import java.util.*;

public class test {
    public static void main(String[] args) {
        Scanner in = new Scanner(;
        Deque deque = new ArrayDeque<>();
        HashSet<Integer> set = new HashSet<>();

        int n = in.nextInt();
        int m = in.nextInt();
        int max = Integer.MIN_VALUE;

        for (int i = 0; i < n; i++) {
            int input = in.nextInt();


            if (deque.size() == m) {
                if (set.size() > max)
                    max = set.size();

                int first = (int) deque.remove();
                if (!deque.contains(first))

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