Question

To the TwoDArray class, add a method called transpose() that generates the transpose of a 2D array with the same number of rows and columns (i.e., a square matrix). Add appropriate code in main() of the TwoDArrayApp class to execute the transpose() method and use the display() method to print the transposed matrix.

/**
* TwoDArray.java
*/

public class TwoDArray
{
   private int a[][];
   private int nRows;

public TwoDArray(int maxRows, int maxCols)        //constructor
{
   a = new int[maxRows][maxCols];
   nRows = 0;
}
//******************************************************************
   public void insert (int[] row)
   {
       a[nRows] = row;
       nRows++;
   }
//******************************************************************
   public void display()
   {
       for (int i = 0; i < nRows; i++)
       {
           for (int j = 0; j < a[0].length; j++)
               System.out.format("%5d", a[i][j]);
           System.out.println(" ");
       }
   }
}

public class TwoDArrayApp{
  
public static void main(String[] args )
{
   int maxRows = 20;
   int maxCols = 20;
  
   TwoDArray arr = new TwoDArray(maxRows, maxCols);    
   int b[][] = {{1, 2, 3, 4}, {11, 22, 33, 44}, {2, 4, 6, 8},{100, 200, 300, 400}};
  
  
   arr.insert(b[0]); arr.insert(b[1]); arr.insert(b[2]); arr.insert(b[3]);
  

  
   System.out.println("The original matrix: ");
   arr.display();
  
   System.out.println("Column sum: ");
   arr.sumCols();  
  
   System.out.println(" ");
   System.out.println("\nThe matrix after being transposed: ");
   arr.transpose();
  
  
  

  
}
}

Answer 1

/**
 * TwoDArray.java
 */
public class TwoDArray {
    private int a[][];
    private int nRows;

    public TwoDArray(int maxRows, int maxCols) //constructor
    {
        a = new int[maxRows][maxCols];
        nRows = 0;
    }

    //******************************************************************
    public void insert(int[] row) {
        a[nRows] = row;
        nRows++;
    }

    //******************************************************************
    public void display() {
        for (int i = 0; i < nRows; i++) {
            for (int j = 0; j < a[0].length; j++)
                System.out.format("%5d", a[i][j]);
            System.out.println(" ");
        }
    }

    public void sumCols() {
        for (int i = 0; i < a[0].length; i++) {
            int sum = 0;
            for (int j = 0; j < nRows; j++) {
                sum += a[j][i];
            }
            System.out.println("Sum of all elements of column " + i + " is " + sum);
        }
    }

    public TwoDArray transpose() {
        TwoDArray result = new TwoDArray(a[0].length, nRows);
        for (int i = 0; i < a[0].length; i++) {
            int[] row = new int[nRows];
            for (int j = 0; j < nRows; j++)
                row[j] = a[j][i];
            result.insert(row);
        }
        return result;
    }
}

/**
 * TwoDArrayApp.java
 */
public class TwoDArrayApp {
    public static void main(String[] args) {
        int maxRows = 20;
        int maxCols = 20;

        TwoDArray arr = new TwoDArray(maxRows, maxCols);
        int b[][] = {{1, 2, 3, 4}, {11, 22, 33, 44}, {2, 4, 6, 8}, {100, 200, 300, 400}};


        arr.insert(b[0]);
        arr.insert(b[1]);
        arr.insert(b[2]);
        arr.insert(b[3]);


        System.out.println("The original matrix: ");
        arr.display();

        System.out.println("Column sum: ");
        arr.sumCols();

        System.out.println(" ");
        System.out.println("\nThe matrix after being transposed: ");
        arr.transpose();
        arr.display();
    }
}