Java Program for Magic Square

JAVA TASK:

Create Java application capable of solving a 3×3 square filled with digits in order to determine if it is a magic square. User should be able to access such functionality as: filling the square with numeric values, checking the values in the current square, and checking the current square for being a magic square.

SOLUTION:

In this sample we are going to use arrays, so we will proceed with importing java.util.Arrays. The main loop of our program will correspond to four actions: “new” (begin filling a new int square), “show” (display the values of the current square), “info” (determine the sums of digits in rows, columns, and diagonals of square, in order to determine if it’s a magic one), and “exit” (exits the main loop and application).

Obviously, until we haven’t filled a square, “show” and “info” commands should not be available. We will use a boolean variable as flag to enable these two later:

//flag which determines whether sqr array is filled with numbers
boolean existingsqr = false;

This will result in the following structure for messages informing the user:

System.out.println("Input \"new\" to start filling new 3x3 square");
if(existingsqr)
	System.out.println("Input \"show\" to display existing square");     
if(existingsqr)
	System.out.println("Input \"info\" to display info about existing square");    
System.out.println("Input \"quit\" for exiting the application");

We can fill a new square with:

System.out.println("Input 9 numbers ");

for (int i = 0; i < sqrsize; i++)
{
    for (int j = 0; j < sqrsize; j++)
    {
        System.out.println("Input value for row " + (i+1) + " column " + (j+1));
        sqr[i][j] = in.nextInt();
    }
}

After this we enable the aforementioned flag:

existingsqr = true;

We can display the current square with:

System.out.println("Current square:");
System.out.println(sqr[0][0]+" " +sqr[0][1]+" " +sqr[0][2]);
System.out.println(sqr[1][0]+" " +sqr[1][1]+" " +sqr[1][2]);
System.out.println(sqr[2][0]+" " +sqr[2][1]+" " +sqr[2][2]);  

The we can count the sums of elements of this square (rows, columns, and diagonals respectively) with:

int[] sums_rows = new int[sqrsize];
Arrays.fill(sums_rows, 0);

int[] sums_columns = new int[sqrsize];
Arrays.fill(sums_columns, 0);

int[] sums_diagonals = new int[2];
Arrays.fill(sums_diagonals, 0);

for (int i = 0; i < sqrsize; i++) {
    for (int j = 0; j < sqrsize; j ++) {
        sums_rows[i] += sqr[i][j];
    }
    System.out.println("the sum of elements of row " + (i+1) + " :\n" + sums_rows[i]);
}
for (int j = 0; j < sqrsize; j++) {
    for (int i = 0; i < sqrsize; i ++) {
        sums_columns[j] += sqr[i][j];
    }
    System.out.println("the sum of elements of column " + (j+1) + " :\n" + sums_columns[j]);
}

for (int i = 0; i < sqrsize; i++) {
    sums_diagonals[0] += sqr[i][i];
}
System.out.println("the sum of diagonal 1 " + "\n" + sums_diagonals[0]);

for (int i = 0; i < sqrsize; i++) {
    sums_diagonals[1] += sqr[i][(sqrsize-1)-i];
}
System.out.println("the sum of diagonal 2 " + "\n" + sums_diagonals[1]);

After this we need to compare the sums we have just found. We will assume that it is magic square straight away:

boolean isMagicSquare = true;

Then once even a one sum of the ones found isn’t equal to the others, we assume that the square is not a magic one:

int comparedSum = sums_rows[0];
for (int i = 1; i < sqrsize; i++) {
  isMagicSquare = isMagicSquare && (comparedSum == sums_rows[i]);
}
for (int i = 0; i < sqrsize; i++) {
  isMagicSquare = isMagicSquare && (comparedSum == sums_columns[i]);
}
for (int i = 0; i < 2; i++) {
  isMagicSquare = isMagicSquare && (comparedSum == sums_diagonals[i]);
}

Therefore, the final code for our application (with console window format in mind) will look like this:

package testproject3;

//importing Scanner class
import java.util.Scanner;  

//importing Array tools
import java.util.Arrays;

//importing packages used for detecting key events
import java.awt.Toolkit;

/**
 *
 * @author User
 */
public class TestProject3 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        
        //a strings type variable used to store text
        String textvar = "";
        //flag which determines whether sqr array is filled with numbers
        boolean existingsqr = false;
        //array for storing magic square
        int [] [] sqr = new int [3][3];
        //used in for cycles
        int sqrsize = sqr.length;
        //creating new scanner object which takes InputStream as parameter
        Scanner in = new Scanner(System.in);
        
        do
        { 
            System.out.println("Input \"new\" to start filling new 3x3 square");
            if(existingsqr)System.out.println("Input \"show\" to display existing square");      
            if(existingsqr)System.out.println("Input \"info\" to display info about existing square");      
            System.out.println("Input \"quit\" for exiting the application");
                 
            textvar = in.nextLine();
            if("new".equals(textvar))
            {
                System.out.println("Input 9 numbers ");
                
                for (int i = 0; i < sqrsize; i++)
                {
                    for (int j = 0; j < sqrsize; j++)
                    {
                        System.out.println("Input value for row " + (i+1) + " column " + (j+1));
                        sqr[i][j] = in.nextInt();
                    }
                }
                existingsqr = true;
                System.out.println("Thanks!");
                System.out.println();  
            }  
            else if("show".equals(textvar) && existingsqr)
            {
                System.out.println("Current square:");
                System.out.println(sqr[0][0]+" " +sqr[0][1]+" " +sqr[0][2]);
                System.out.println(sqr[1][0]+" " +sqr[1][1]+" " +sqr[1][2]);
                System.out.println(sqr[2][0]+" " +sqr[2][1]+" " +sqr[2][2]);               
            }
            else if("info".equals(textvar) && existingsqr)
            {                
                int[] sums_rows = new int[sqrsize];
                Arrays.fill(sums_rows, 0);
                                
                int[] sums_columns = new int[sqrsize];
                Arrays.fill(sums_columns, 0);
                
                int[] sums_diagonals = new int[2];
                Arrays.fill(sums_diagonals, 0);

                for (int i = 0; i < sqrsize; i++) {
                    for (int j = 0; j < sqrsize; j ++) {
                        sums_rows[i] += sqr[i][j];
                    }
                    System.out.println("the sum of elements of row " + (i+1) + " :\n" + sums_rows[i]);
                }
                for (int j = 0; j < sqrsize; j++) {
                    for (int i = 0; i < sqrsize; i ++) {
                        sums_columns[j] += sqr[i][j];
                    }
                    System.out.println("the sum of elements of column " + (j+1) + " :\n" + sums_columns[j]);
                }
                
                for (int i = 0; i < sqrsize; i++) {
                    sums_diagonals[0] += sqr[i][i];
                }
                System.out.println("the sum of diagonal 1 " + "\n" + sums_diagonals[0]);
                
                for (int i = 0; i < sqrsize; i++) {
                    sums_diagonals[1] += sqr[i][(sqrsize-1)-i];
                }
                System.out.println("the sum of diagonal 2 " + "\n" + sums_diagonals[1]);
                
                boolean isMagicSquare = true;
                
                int comparedSum = sums_rows[0];
                for (int i = 1; i < sqrsize; i++) {
                  isMagicSquare = isMagicSquare && (comparedSum == sums_rows[i]);
                }
                for (int i = 0; i < sqrsize; i++) {
                  isMagicSquare = isMagicSquare && (comparedSum == sums_columns[i]);
                }
                for (int i = 0; i < 2; i++) {
                  isMagicSquare = isMagicSquare && (comparedSum == sums_diagonals[i]);
                }

                if(isMagicSquare)
                    System.out.println("All sums are equal, this is a magic square");
                else
                    System.out.println("The sums are not equal, so this isn't a magic square");    
                
                System.out.println();  
            }
            else if(!"quit".equals(textvar))
            {
                //cleans screen by pushing text off screen
                for(int clear = 0; clear < 1000; clear++)
                {
                    System.out.println("\b") ;
                }
            }
        }        
        while (!"quit".equals(textvar)); 
        //loop will repeat until textvar reaches the necessary value
    }
    
}

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