ISC Computer Practical 2015 Question 2

Write a program to declare a square matrix A[][] of order MxM where
‘M’ is the number of rows and the number of coloumns, such that M is greater than 2 and less than 10. Accept the value of M as user input. Display an appropriate message for invalid input. Allow the user to input integers into this matrix. Perform the following tasks:

(a) Display the original matrix.

(b) Rotate the matrix 90 degree clockwise as shown below:

Original matrix   Rotated matrix
 1 2 3               7 4 1
 4 5 6               8 5 2
 7 8 9               9 6 3

(c) Find the sum of the elements of the four corner elements.

Test your program for the following data and some random data.

Example 1:

INPUT: M = 3
 3 4 9
 2 5 8
 1 6 7
OUTPUT:
ORIGINAL MATRIX
 3 4 9
 2 5 8
 1 6 7
MATRIX AFTER ROTATION
 1 2 3
 6 5 4
 7 8 9
Sum of corner elements = 20

Example 2

INPUT: M = 4
 1 2 4 9
 2 5 8 3
 1 6 7 4
 3 7 6 5
OUTPUT:
ORIGINAL MATRIX
 1 2 4 9
 2 5 8 3
 1 6 7 4
 3 7 6 5
MATRIX AFTER ROTATION
  3 1 2 1
  7 6 5 2
  6 7 8 4
  5 4 3 9
Sum of corner elements = 18

Example 3

INPUT: M = 14
OUTPUT:
SIZE IS OUT OF RANGE

The Java implementation for “Rotation of matrix by 90 degree clockwise” is as follows:

import java.util.*;
class Q2{
    public static int[][] rotate( int a[][] ){
        int n=a.length;
        int temp;
        for (int i=0; i<n/2; i++){
            for (int x=i; x<n-i-1; x++){
                temp=a[n-x-1][i];
                a[n-x-1][i]=a[n-i-1][n-x-1];
                a[n-i-1][n-x-1]=a[x][n-i-1];
                a[x][n-i-1]=a[i][x];
                a[i][x]=temp;
            }
        }
        return a;
    }

    public static void displayArray( int ar[][] ){
        for(int row=0; row<ar.length; row++){
            for( int col=0; col<ar[row].length;col++){
                System.out.print(ar[row][col]+"\t");
            }
            System.out.println();
        }
    }

    public static void main( String args[] ){
        Scanner sc = new Scanner( System.in );
        System.out.print("INPUT:\tM = ");
        int M = sc.nextInt();
        if( M>2 && M<10 ){
            int A[][] = new int[M][M];
            for(int row=0; row<A.length; row++){
                for( int col=0; col<A[row].length;col++){
                    A[row][col]=sc.nextInt();
                }
            }
            System.out.println("OUTPUT:\nORIGINAL MATRIX");
            displayArray(A);
            A = rotate(A);
            System.out.println("OUTPUT:\nMATRIX AFTER ROTATION");
            displayArray(A);
            int cornerSum = A[0][0]+A[0][M-1]+A[M-1][0]+A[M-1][M-1];
            System.out.println("Sum of corner elements = " + cornerSum);
        }else{
            System.out.println("OUTPUT:\nSIZE OUT OF RANGE");
        }
    }
}

In the above program on “Rotation of matrix by 90 degree clockwise” was asked in the ISC Computer Practical  2015.

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Vinay Singh

Computer Teacher at Saint John's Academy
I am a GNU/Linux enthusiast and a computer science teacher by profession based at Allahabad, India. My hobbies include reading (mostly computer related stuff) and photography.
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