## Counting Repeated Elements in an Array in Java

As a programming language, Java has many functions that make it one of the most popular programming languages in the world. One of the most common programming problems that developers face when programming in Java is counting repeated elements in an array.

In this article, we will explore the methods used to count duplicates in arrays in Java and how to implement them. We will start by looking at the two main methods for counting duplicates in unsorted and sorted arrays, respectively.

We will then go on to consider the implementation of these methods in Java.

## Method for Counting Duplicates in an Unsorted Array

The first method we will consider is for counting duplicates in an unsorted array in Java. An unsorted array is a list of elements that have not been arranged in a specific order.

Suppose you have an array of integers and need to count the number of repeated elements. To do this, you must create a temporary array where the elements are sorted.

Once the array is sorted, you can loop through the temporary array and compare each element to the one before it. If the two elements match, then you know that the current element is a duplicate.

You must then use a flag variable to mark that element so that it is not counted again.

## Method for Counting Duplicates in a Sorted Array

The second method of counting duplicates is used for arrays that are already sorted. In a sorted array, elements are arranged in a specific order.

Therefore, the method for counting duplicates in sorted arrays is simpler than that used in an unsorted array. You can use a variable to keep track of repeat counts and a loop to traverse through each element of the sorted array.

When an element is repeated, you add one to the repeat count variable. You continue this process until the last element of the array is reached.

## Getting Input and Creating a Temporary Array

Now we will consider how to implement the methods we’ve discussed. To start, you must create a Java program that takes input from the user.

The user’s input must be stored in an array. You must then create a temporary array that is the same size as the input array.

The elements in the input array must be copied to the temporary array.

## Traversing through the Input Array and Counting Duplicates

Now that we have the input and temporary arrays, we can start traversing through the input array and comparing elements. For an unsorted array, you must be careful to not double-count duplicates.

To avoid this, mark the current element in the temporary array when you find a duplicate. For a sorted array, use a simple loop to traverse through the array.

Whenever an element matches the previous element, increase the repeat count variable by one.

## Displaying the Total Repeated Elements and the Repeated Elements Themselves

After counting the duplicates, the next step is to display the number and the elements that are repeated. You can do this by using another loop to traverse through the temporary array.

When you find a marked element, output its value as a repeated element.

## Conclusion

In conclusion, counting repeated elements in arrays in Java is a fundamental problem that developers often face. The two primary methods used to count duplicates are for unsorted and sorted arrays.

To implement these methods, you must traverse through the input array, use a temporary array, and employ a flag variable to avoid double-counting duplicates in unsorted arrays. When you have counted the duplicates, display the total number of elements that are repeated and the repeated values themselves.

By following these instructions, you will be able to quickly and efficiently count duplicates in arrays using Java.

## Simplifying the Code for Sorted Arrays

When working with sorted arrays in Java, counting duplicates is a much simpler problem than dealing with unsorted arrays. This is because elements that are the same will always be next to each other in the sorted array.

Therefore, there is no need to compare each element to all others in the array. In this article, we will discuss how to simplify the code for counting duplicates in sorted arrays.

## Creating a Program Specifically for Sorted Arrays

The first way to simplify the code for sorted arrays is to create a program that is specifically designed to handle sorted arrays. This program can be different from the one used for unsorted arrays because the approaches to each problem are different.

For example, you do not need to sort the array before counting duplicates in a sorted array. This can save a lot of time and resources.

## Comparing Only Adjacent Elements to Count Duplicates

Another way to simplify the code for sorted arrays is to compare only adjacent elements to count duplicates. Since sorted arrays have all their elements arranged in specific orders, identical elements will always be adjacent to each other.

This means that there is no need to compare each element to all others in the array. Comparing adjacent elements will suffice.

Let us consider how to implement this in Java. The process involves creating a loop to traverse through the sorted array and compare each element to the one next to it.

If the two elements match, then the count of repeated elements must be updated. By using this method, you can eliminate the need to use a temporary array, thereby saving time and resources.

## Example Program for Counting Duplicates in Sorted Arrays

To further illustrate this point, here is an example program in Java for counting duplicates in a sorted array:

“`

import java.util.Scanner;

public class CountDuplicates {

public static void main(String[] args) {

int n, count = 0;

Scanner input = new Scanner(System.in);

System.out.println(“Enter number of elements in the array:”);

n = input.nextInt();

int arr[] = new int[n];

System.out.println(“Enter elements of the array:”);

for(int i = 0; i < n; i++)

{

arr[i] = input.nextInt();

}

for(int i = 0; i < n-1; i++)

{

if(arr[i] == arr[i+1])

{

count++;

}

}

System.out.println(“Total Duplicate Elements: ” + count);

}

}

“`

In this program, the user is asked to enter the number of elements in the array. The elements of the sorted array are then entered.

A loop is used to traverse through the array and compare each element to the next one. If the elements match, then the count of duplicates is incremented.

Finally, the program outputs the total duplicate elements in the array.

## Conclusion

In conclusion, counting duplicates in sorted arrays is a much simpler problem than in unsorted arrays. Since the elements in a sorted array are arranged in specific orders, identical elements will be adjacent to each other.

Therefore, there is no need to compare each element to all others in the array. By comparing adjacent elements, you can simplify the code for counting duplicates in sorted arrays.

The example program provided in this article shows how to implement this method in Java, and it can be used as a foundation for more complex programs. In this article, we have discussed the two main methods used to count duplicates in arrays in Java, which are employed for unsorted and sorted arrays, respectively.

We have examined how to implement these methods in Java code, and we have also explored the ways in which the code for counting duplicates in sorted arrays can be further simplified. By comparing adjacent elements in sorted arrays and creating programs that are specifically designed to handle sorted arrays, we can eliminate the need to sort temporary arrays and reduce time and resources.

Overall, counting duplicates in arrays is an essential programming problem, and familiarity with these methods is a valuable asset for Java programmers.