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# Java Program to check for Scalar Matrix

#### Question:

Write a Program in Java to input a 2-D square matrix and check whether it is a Scalar Matrix or not.

Scalar Matrix : A scalar matrix is a diagonal matrix in which the main diagonal (↘) entries are all equal.

Example:

$\begin{bmatrix} 5 & 0 & 0 & 0 \\ 0 & 5 & 0 & 0 \\ 0 & 0 & 5 & 0 \\ 0 & 0 & 0 & 5 \end{bmatrix}$

#### Solution:

/**
* The class ScalarMatrix inputs a Matrix and checks whether it is a scalar matrix or not
* @author : www.guideforschool.com
* @Program Type : BlueJ Program - Java
*/

import java.util.*;
class ScalarMatrix
{
public static void main(String args[])throws Exception
{
Scanner sc=new Scanner(System.in);
System.out.print("Enter the size of the matrix : ");
int m=sc.nextInt();
int A[][]=new int[m][m];

/* Inputting the matrix */
for(int i=0;i<m;i++)
{
for(int j=0;j<m;j++)
{
System.out.print("Enter an element : ");
A[i][j]=sc.nextInt();
}
}

/* Printing the matrix */
System.out.println("*************************");
System.out.println("The Matrix is : ");
for(int i=0;i<m;i++)
{
for(int j=0;j<m;j++)
{
System.out.print(A[i][j]+"\t");
}
System.out.println();
}
System.out.println("*************************");

int p = 0, q = 0, x = A[0][0]; // 'x' is storing the 1st main diagonal element

for(int i=0;i<m;i++)
{
for(int j=0;j<m;j++)
{
/* Checking that the matrix is diagonal or not */
if(i!=j && A[i][j]!=0) // All non-diagonal elements must be zero
{
p=1;
break;
}
/* Checking the matrix for scalarity */
// All main diagonal elements must be equal to 'x' and non-zero
if(i==j && (A[i][j]==0 || A[i][j]!=x))
{
q=1;
break;
}
}
}

if(p==0 && q==0)
System.out.println("The matrix is scalar");
else
System.out.println("The matrix is not scalar");
}
}

#### Output:

Enter the size of the matrix : 4
Enter an element : 5
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 5
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 5
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 0
Enter an element : 5
*************************
The Matrix is :
5 0 0 0
0 5 0 0
0 0 5 0
0 0 0 5
*************************
The matrix is Scalar

## [Question 2] ISC 2017 Computer Practical Paper Solved – Quiz Result

Solution of Program 2 of ISC 2017 Computer Science Paper 2 (Practical) Exam. Java program to input the answers of each participant row-wise and calculate their marks