Java Program to Print Common Elements in all Rows of a Matrix

In this article we are going to see how we can write a program to find common element in all row of a given matrix.

Java Program to Print Common Elements in all Rows of 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.

Let’s see different ways to common element in all row  of a given matrix.

Method-1: Java Program to Print Common Elements in all Rows of a Matrix By Static Initialization of Array Elements

Approach :

  • Declare and Initialize a matrix.
  • Define ele with elements as keys and their count as values.
  • Insert all elements of first row into ele with 1 as their values.
  • For remaining rows, check presence of each element in ele.
  • If element is present in ele and its count is equal to ‘x’, then increment its count by 1.
  • Print ele having common elements.

Program :

import java.util.*;
import java.util.Map.Entry;

public class Main 
{
   public static void main(String args[])
   {
      int mat[][] = { { 1, 2, 3 },{ 4, 3, 1 },{ 1, 0, 3 } }; 
      
        //Define ele with elements as keys and their count as values
        HashMap<Integer, Integer> ele = new HashMap<>();
        
        //Insert all elements of first row into ele with 1 as their values
        for (int y = 0; y < 3; y++)
            ele.put(mat[0][y], 1);
            
        //For remaining rows, check presence of each element in ele
        for (int x = 1; x < 3; x++) 
            for (int y = 0; y < 3 ; y++) 
                //If element is present in ele and it's count is equal to 'x',
                //then increment its count by 1
                if(ele.containsKey(mat[x][y]) && ele.get(mat[x][y]) == x)
                        ele.put(mat[x][y], x+1);
                        
        //Printing ele having common elements
        Set<Entry<Integer, Integer>> en = ele.entrySet();
        System.out.println("Common Elements In All Rows : ");
        for (Entry<Integer, Integer> e : en) 
            if (e.getValue() == 3) 
                System.out.print(e.getKey() + " ");
    } 
}
Output:

Common Elements In All Rows : 
1 3

Method-2: Java Program to Print Common Elements in all Rows of a Matrix By Dynamic Initialization of Array Elements

Approach:

  • Take user input of a matrix.
  • Define ele with elements as keys and their count as values.
  • Insert all elements of first row into ele with 1 as their values.
  • For remaining rows, check presence of each element in ele.
  • If element is present in ele and its count is equal to ‘x’, then increment its count by 1.
  • Print ele having common elements.

Program:

import java.util.*;
import java.util.Map.Entry;
public class Main 
{
   public static void main(String args[])
   {
       Scanner sc = new Scanner(System.in);
       
        // Initializing the 3X3 matrix i.e. 2D array
        int mat[][] = 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++)
                mat[row][col] = sc.nextInt();
                
        //Define ele with elements as keys and their count as values
        HashMap<Integer, Integer> ele = new HashMap<>();
        
        //Insert all elements of first row into ele with 1 as their values
        for (int y = 0; y < 3; y++)
            ele.put(mat[0][y], 1);
            
        //For remaining rows, check presence of each element in ele
        for (int x = 1; x < 3; x++) 
            for (int y = 0; y < 3 ; y++) 
                //If element is present in ele and it's count is equal to 'x',
                //then increment its count by 1
                if(ele.containsKey(mat[x][y]) && ele.get(mat[x][y]) == x)
                        ele.put(mat[x][y], x+1);
                        
        //Printing ele having common elements
        Set<Entry<Integer, Integer>> en = ele.entrySet();
        System.out.println("Common Elements In All Rows : ");
        for (Entry<Integer, Integer> e : en) 
            if (e.getValue() == 3) 
                System.out.print(e.getKey() + " ");
    } 
}

Output:

Enter matrix elements
Common Elements In All Rows : 
1 3

Beginners and experienced programmers can rely on these Best Java Programs Examples and code various basic and complex logics in the Java programming language with ease.

Leave a Comment