Question

Download the SwapMultidimensional.java file, and open it in jGrasp (or a text editor of your choice). This program contains two methods which you will need to write:

• swapRows: Swaps the contents of two rows, given a two-dimensional array and the indices of the rows to swap.
• swapCols: Swaps the contents of two columns, given a two-dimensional array and the indices of the columns to swap.

main contains some code which will call swapRows and swapCols, for the purpose of informal testing. With this in mind, example output of the program is below:

Before swapping rows 0 and 2:
0 1 2
3 4 5
6 7 8
After swapping rows 0 and 2:
6 7 8
3 4 5
0 1 2

Before swapping columns 1 and 2:
9 8 7
6 5 4
3 2 1
After swapping columns 1 and 2:
9 7 8
6 4 5
3 1 2

-----------------------------------------------------------------------

public class SwapMultidimensional {
    // You must write TWO methods:
    //
    // 1.) A method named "swapRows" that swaps the
    //     contents of two rows in a given two-dimensional
    //     array. This method MUST NOT use loops. As a hint,
    //     since a two-dimensional array is just an array of
    //     arrays where each inner array is a row, this means
    //     that you can swap entire rows just by swapping two
    //     elements of the outer array.
    //
    // 2.) A method named "swapCols" that swaps the contents
    //     of two columns in a given two-dimensional array.
    //     This method MUST use a loop.
    // TODO - write your code below this comment.


    // DO NOT MODIFY print2D!
    public static void print2D(int[][] array) {
        for (int row = 0; row < array.length; row++) {
            for (int col = 0; col < array[row].length - 1; col++) {
                System.out.print(array[row][col] + " ");
            }
            System.out.println(array[row][array[row].length - 1]);
        }
    }

    // DO NOT MODIFY main!
    public static void main(String[] args) {
        int[][] example1 = new int[][]{ new int[]{0, 1, 2},
                                        new int[]{3, 4, 5},
                                        new int[]{6, 7, 8} };
        int[][] example2 = new int[][]{ new int[]{9, 8, 7},
                                        new int[]{6, 5, 4},
                                        new int[]{3, 2, 1} };
        System.out.println("Before swapping rows 0 and 2:");
        print2D(example1);
        swapRows(example1, 0, 2);
        System.out.println("After swapping rows 0 and 2:");
        print2D(example1);

        System.out.println("\nBefore swapping columns 1 and 2:");
        print2D(example2);
        swapCols(example2, 1, 2);
        System.out.println("After swapping columns 1 and 2:");
        print2D(example2);
    }
}

Answer 1

If you have any doubts, please give me comment...

public class SwapMultidimensional {

// You must write TWO methods:

//

// 1.) A method named "swapRows" that swaps the

// contents of two rows in a given two-dimensional

// array. This method MUST NOT use loops. As a hint,

// since a two-dimensional array is just an array of

// arrays where each inner array is a row, this means

// that you can swap entire rows just by swapping two

// elements of the outer array.

//

public static void swapRows(int[][] arr, int r1, int r2){

int temp[] = arr[r1];

arr[r1] = arr[r2];

arr[r2] = temp;

}

// 2.) A method named "swapCols" that swaps the contents

// of two columns in a given two-dimensional array.

// This method MUST use a loop.

// TODO - write your code below this comment.

public static void swapCols(int[][] arr, int c1, int c2){

int rLen = arr.length;

int temp[] = new int[rLen];

for(int i=0; i<rLen; i++)

temp[i] = arr[i][c1];

for(int i=0; i<rLen; i++)

arr[i][c1] = arr[i][c2];

for(int i=0; i<rLen; i++)

arr[i][c2] = temp[i];

}

// DO NOT MODIFY print2D!

public static void print2D(int[][] array) {

for (int row = 0; row < array.length; row++) {

for (int col = 0; col < array[row].length - 1; col++) {

System.out.print(array[row][col] + " ");

}

System.out.println(array[row][array[row].length - 1]);

}

}

// DO NOT MODIFY main!

public static void main(String[] args) {

int[][] example1 = new int[][]{ new int[]{0, 1, 2},

new int[]{3, 4, 5},

new int[]{6, 7, 8} };

int[][] example2 = new int[][]{ new int[]{9, 8, 7},

new int[]{6, 5, 4},

new int[]{3, 2, 1} };

System.out.println("Before swapping rows 0 and 2:");

print2D(example1);

swapRows(example1, 0, 2);

System.out.println("After swapping rows 0 and 2:");

print2D(example1);

System.out.println("\nBefore swapping columns 1 and 2:");

print2D(example2);

swapCols(example2, 1, 2);

System.out.println("After swapping columns 1 and 2:");

print2D(example2);

}

}