in Java I have to check if a given matrix is a latin square or not

Question

my teacher has given us a matrix and we are supposed to write a code that checks if it is a latin square or not. I have all of the pieces but I am having trouble putting them in order so they work. this is what she has given us to read the matrix she has created.

The text file is matrix.txt, here is what it contains.

3

1 2 3

3 1 2

2 3 1

As you can see this is a latin square, however, she said we can change the matrix to make sure it works with the other problems she gave us.

     import java.io.File;
     import java.io.FileNotFoundException;
     import java.util.Scanner;
     public class Multidim {

public static void main(String args[]){
    int matrix[][] = initMatrix();
    //printData(matrix); //Uncomment to print array

    /////YOUR MAIN CODE HERE/////



}

///PLACE YOUR METHODS HERE

public static int[][] initMatrix(){
    int matrix[][];
    Scanner filein = null;
    try {
        filein = new Scanner(new File("matrix.txt"));
        int numRows = Integer.parseInt(filein.nextLine());
        matrix = new int[numRows][];
        parseData(matrix, filein);
        filein.close();
        return matrix;
    } catch (FileNotFoundException e) {
        System.out.println(e.getMessage());
        if(filein != null)
            filein.close();
        return null;
    }
}

public static void parseData(int matrix[][], Scanner in){
    for(int r = 0; r < matrix.length; r++){
        String splitLine[] = in.nextLine().split(" ");
        matrix[r] = new int[splitLine.length];
        for(int c = 0; c < matrix[r].length; c++){
            matrix[r][c] = Integer.parseInt(splitLine[c]);
        }
    }
}

public static void printData(int matrix[][]){
    for(int r = 0; r < matrix.length; r++){
        for(int c = 0; c < matrix[r].length; c++){
            System.out.print(matrix[r][c] + " ");
        }
        System.out.println();
    }
}

}

This is the code I have currently. Where does it go?

    public static boolean LatinSquare(int[][]array) {
    for(int i=0;i<array.length;i++) {
        for(int j=0; j<array[i].length; j++)  {
           if(i!=j)   {
               return false;
           }
        }
    }
    return true;
}
public boolean DuplicatesInRows(int[][]array) {
    for (int i=0; i<array.length; i++)  {
        for (int j=0;j<array[i].length; j++) {
            int num=array[i][j];
            for(int col =j+1; col<array.length; col++) {
                if(num==array[i][col])  {
                    return true;
                }
            }
        }
    }
    return false;
   }
public boolean DuplicatesInCol(int[][]array) {
    for(int i=0;i<array.length; i++)  {
        for(int j=0; j<array.length; j++)  {
            for(int k=1; k<array.length; k++)  {
                if (array[i][j+k]==array[i][j])  {
                    if (array[i][j]!=0)  {
                        return true;
                    }
                }
            }
        }
    }
    return false;
    }

And I have no idea where this goes either...

  if(LatinSquare(matrix)==false)
  System.out.println("This is not a Latin Square");
  else
  System.out.println("This is a Latin Square");

Answer 1

Here is how I would do it

Multidim.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Multidim 
{

    public static void main(String args[])
    {
        int matrix[][] = initMatrix();
        // printData(matrix); //Uncomment to print array
        if(latinSquare(matrix))
        {
            System.out.println("This is a Latin Square");
        }
        else
        {
            System.out.println("This is not a Latin Square");          
        } 
    }

    public static boolean latinSquare(int[][] array) 
    {
        for (int i = 0; i<array.length ;i++) 
        {
            // check for duplicates in each row
            if(duplicates(array[i]))
            {
                return false;
            }

            // create a column array
            int[] column = new int[array[i].length]; 
            for(int j = 0; j<array.length; j++)
            {
                column[j] = array[j][i]; // could throw an exception if the input file isn't square 3x3, 2x2, 4x4, etc
            }

            // check for duplicates in each column
            if(duplicates(column))
            {
                return false;
            }
        }
        return true;
    }

    public static boolean duplicates(int[] array)
    {
        for (int i = 0; i<array.length; i++) 
        {
            for(int j = 0; j<array.length; j++)
            {
                if (i != j && array[i] == array[j])
                {
                    return true;
                }
            }    
        }
        return false;
    }

    ///PLACE YOUR METHODS HERE
    public static int[][] initMatrix()
    {
        int matrix[][];
        Scanner filein = null;
        try 
        {
            filein = new Scanner(new File("matrix.txt"));
            int numRows = Integer.parseInt(filein.nextLine());
            matrix = new int[numRows][];
            parseData(matrix, filein);
            filein.close();
            return matrix;
        } 
        catch (FileNotFoundException e) 
        {
            System.out.println(e.getMessage());
            if(filein != null)
            {
                filein.close();
            }
            return null;
        }
    }

    public static void parseData(int matrix[][], Scanner in)
    {
        for(int r = 0; r < matrix.length; r++)
        {
            String splitLine[] = in.nextLine().split(" ");
            matrix[r] = new int[splitLine.length];
            for(int c = 0; c < matrix[r].length; c++)
            {
                matrix[r][c] = Integer.parseInt(splitLine[c]);
            }
        }
    }

    public static void printData(int matrix[][])
    {
        for(int r = 0; r < matrix.length; r++)
        {
            for(int c = 0; c < matrix[r].length; c++)
            {
                System.out.print(matrix[r][c] + " ");
            }
            System.out.println();
        }
    }
}

matrix.txt

3
1 2 3
3 1 2
2 3 1

Note that your methods should follow Oracle's code conventions

Methods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized.

That is why I changed LatinSquare to latinSquare