Question

Here are the directions:

Implement the following method so that it prints all even-valued elements from the even-indexed rows of arr, and all odd-valued elements from the odd-indexed rows of arr.

Elements of the same row should appear on the same line, separated by a space. Elements of different rows should appear on different lines.

Example:

int[][] arr = {{1, 2, 3},
               {1, 2, 3}
               {4, 5, 6}};

printOddEvens(arr);

Should print:

2

1 3

4 6

This is what I have, way off, but in the right direction:

(I know the prints are wrong.)

public static void main(String[] args) {
    int arr[][] = {{1,2,3},{1,2,3},{4,5,6}};

    for (int i = 0; i < arr.length; i++) {
        for (int j = 0; j < arr[i].length; j++) {
            if (i % 2 == 0) {
                System.out.println(arr[i][j]);
            }
            if (!i % 2 == 0) {
                System.out.println(arr[i][j]);
            }
        }
    }
}

Answer 1

Here is the solution:

public class ArrayFilter {

    private static int[][] arr = new int[][] { {1, 2, 3}, {1, 2, 3}, {4, 5, 6}};

    private static void printOddEvens(int[][] matrix) {
        for (int row = 0; row < matrix.length; row++) {
            for (int col = 0; col < matrix[row].length; col++) {
                // rowIndex + value is only even when both are odd or both are even
                // the modulo (%) operator returns the remainder of the division
                if ((row + matrix[row][col]) % 2 == 0) {
                    System.out.print(matrix[row][col] + " ");
                }
            }
            System.out.println();
        }
    }

    public static void main(String[] args) {
        printOddEvens(arr);
    }
}

One less future competitor for my job I guess (-;