Question

In java run through eclipse

/**
   *
   * Given a square array, determines if it is diagonal
   * That is, returns true if all values in the array are 0
   * except the main diagonal. The main diagonal is entries of the form
   * data[i][j] where i == j. Elements on the main
   * diagonal can be 0 or any other number.
   *
   * Examples:
   * {{1,0,0},
   * {0,2,0}
   * {0,0,3}} yields true
   *
   * {{1,0,9},
   * {0,2,0},
   * {0,0,3}} yields false because 0,2 is nonzero
   *
   * {{0,0,0},
   * {0,0,0},
   * {0,0,3}} yields true because there can be 0
   * entries on the diagonal if desired
   * @param data input array
   * @return true if it is diagonal, false otherwise
   */
   public static boolean isDiagonal(int[][] data) {
      
       return false;
   }

Answer 1

public class IsDiagonal {


    /**
     * Given a square array, determines if it is diagonal
     * That is, returns true if all values in the array are 0
     * except the main diagonal. The main diagonal is entries of the form
     * data[i][j] where i == j. Elements on the main
     * diagonal can be 0 or any other number.
     * <p>
     * Examples:
     * {{1,0,0},
     * {0,2,0}
     * {0,0,3}} yields true
     * <p>
     * {{1,0,9},
     * {0,2,0},
     * {0,0,3}} yields false because 0,2 is nonzero
     * <p>
     * {{0,0,0},
     * {0,0,0},
     * {0,0,3}} yields true because there can be 0
     * entries on the diagonal if desired
     *
     * @param data input array
     * @return true if it is diagonal, false otherwise
     */
    public static boolean isDiagonal(int[][] data) {
        for (int i = 0; i < data.length; i++) {
            for (int j = 0; j < data[i].length; j++) {
                if (i != j && data[i][j] != 0) {
                    return false;
                }
            }
        }
        return true;
    }

    public static void main(String[] args) {
        System.out.println(isDiagonal(new int[][]{{1, 0, 0}, {0, 2, 0}, {0, 0, 3}}));
        System.out.println(isDiagonal(new int[][]{{1, 0, 9}, {0, 2, 0}, {0, 0, 3}}));
        System.out.println(isDiagonal(new int[][]{{0, 0, 0}, {0, 0, 0}, {0, 0, 3}}));
    }
}