Java Program to Find Unique Elements in a Matrix

In the previous article, we have discussed Java Program to Find Smallest Element in Each Column of a Matrix

In this article we are going to see how we can write a program to find out the unique elements in the matrix in JAVA language.

Java Program to Find Unique Elements in a Matrix

A 3*3 Matrix is having 3 rows and 3 columns where this 3*3 represents the dimension of the matrix. Means there are 3*3 i.e. total 9 elements in a 3*3 Matrix.

Let’s understand it in more simpler way.

                   | A00   A01   A02 |
Matrix A =  | A10   A11   A12 |
                   | A20   A21   A22 | 3*3
  • Matrix A represents a 3*3 matrix.
  • A‘ represents the matrix element
  • Aij‘ represents the matrix element at it’s matrix position/index.
  • i‘ represents the row index
  • j‘ represents the column index
  • Means A00=Aij  where i=0 and j=0,  A01=aij where i=0 and j=1 and like this.
  • Here we have started row value from 0 and column value from 0.

Unique elements are elements that occur only once and doesn’t reappear in the matrix.

For example in the below matrix

2 4 6 
6 9 0
4 2 7

Unix Elements are 9, 0, 7 Because other elements are repeated.

Let’s see different ways to find unique elements in a Matrix.

Method-1: Java Program to Find Unique Elements in a Matrix By Static Initialization of Array Elements

Approach:

  • Initialize and declare one 3×3 array with elements.
  • Use two for loops to iterate the rows and columns .
  • Store the maximum.
  • Create a 1D array of maximum size.
  • Print all elements where the value of the 1D array is 1(i.e. frequency of the element)

Program:

public class matrix
{
    public static void main(String args[])
    {
        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = {{10,15,1},{30,50,7},{1,0,0}};
        int row, col;

        System.out.print("The matrix elements are : ");
        printMatrix(arr);
        System.out.println("The unique elements in the matrix are : ");
        printUnique(arr);

        
    }

    // Method to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
        System.out.print("\n");
    }

    // prints unique elements
    static void printUnique(int arr[][])
    {
        int max =0,flag =0,row,col;
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                if(max<arr[row][col])
                    max = arr[row][col];
        // Stores the unique element
        int temp[]=new int[max+1];
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                temp[arr[row][col]]++;
        //Prints the unique element
        for(row=1;row<=max;row++)
            if(temp[row]==1)
            {
                System.out.print(row + " ");
                flag = 1;
            }
        if(flag==0)
            System.out.println("No unique elements");
    }

}

Output:

The matrix elements are : 
10 15 1 
30 50 7 
1  0 0 
The unique elements in the matrix are : 
7 10 15 30 50

Method-2: Java Program to Find Unique Elements in a Matrix By Dynamic Initialization of Array Elements

Approach:

  • Initialize an array of 3×3.
  • Ask the user for input and store them in the one array using two for loops.
  • Use two for loops to iterate the rows and columns .
  • Store the maximum.
  • Create a 1D array of maximum size.
  • Print all elements where the value of the 1D array is 1(i.e. frequency of the element)

Program:

import java.util.Scanner;
public class matrix{
    public static void main(String args[])
    {
        //Scanner class to take input
        Scanner scan = new Scanner(System.in);

        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = new int[3][3];
        int row, col ;
        
        // Taking matrix input
        System.out.println("\nEnter matrix elements : ");
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                arr[row][col] = scan.nextInt();

        System.out.print("The matrix elements are : ");
        printMatrix(arr);
        System.out.println("The unique elements in the matrix are : ");
        printUnique(arr);

        
    }

    // Function to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
        System.out.print("\n");
    }

    // prints unique elements
    static void printUnique(int arr[][])
    {
        int max =0,flag =0,row,col;
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                if(max<arr[row][col])
                    max = arr[row][col];
        // Stores the unique element
        int temp[]=new int[max+1];
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                temp[arr[row][col]]++;
        //Prints the unique element
        for(row=1;row<=max;row++)
            if(temp[row]==1)
            {
                System.out.print(row + " ");
                flag = 1;
            }
        if(flag==0)
            System.out.println("No unique elements");
    }

}

Output:

Enter matrix elements : 1 2 3 1 4 5 6 2 7 8
The matrix elements are : 
1 2 3 
1 4 5 
6 2 7 
The unique elements in the matrix are : 
3 4 5 6 7

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