In the previous article, we have seen Java Program to Check Diagonally Dominant 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

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