Is there a way of not generating the same number with the method I'm using?

Question

I have to print a bingo board by using a 2D array and the method I'm using makes logical sense but I can't seem ti figure out why it's still generating same numbers. Any thoughts? I've tried the arraylist but it's a 1D array, if theres a probability it can be a 2D can someone please help. *****Updated, so i used a bit of everything and I'm still jammed.

package bingo.arrays.assignment;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;


public class bingoooooooooooooo {

    public static void main(String[] args) {
        int[][] card = new int[5][5];
        display1(card);

    }

    public static void display1(int[][] card) {
        int[] colm = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15};

        int v = 1, z = 15;
        int x = 10000;
       List l = new ArrayList();
        for (int i : colm) {
           l.add(i);
       }
        Collections.shuffle(l);
        //do {
        for (int i = 0; i < 5; i++) {

            for (int j = 0; j < 5; j++) {
                boolean numberFound = false;
                while (!numberFound) {
                    int number1 = (int) (Math.random() * z) + v;

                    if (!checkNumber(number1, card, j)) {
                        break;
                    }

                    card[i][j] = number1;
                    System.out.print("|" + card[i][j]);
                }

//                if (card[i][j] > 25) {
//                x++;
//                }
            }

            v = v + 15;
            z = z + 15;
            System.out.println(" ");

        }
        //}while (true);
    }

public static boolean checkNumber(int number, int[][] card, int j) {

    for(int a = 0; a <= j; a++) {

    if(card[i][a] == number) return false;
  }

  return true;
}






}

Answer 1

Basically, you have overlapping ranges, the number can fall within the range of 0 to z plus v. What's happening is a number is been generate in the very low range, but v isn't large enough to move it beyond the range of the previous set

For example...

z == 130, v == 13

(0.289 * 130) + 31 = 68
(0.304 * 130) + 31 = 70
(0.934 * 130) + 31 = 152
(0.85 * 130) + 31 = 141
(0.902 * 130) + 31 = 148

z == 145, v == 13

(0.731 * 145) + 46 = 152
(0.672 * 145) + 46 = 143
(0.016 * 145) + 46 = 48
(0.292 * 145) + 46 = 88
(0.35 * 145) + 46 = 96

You can see that numbers in both sets are overlapping with each other. The problem only gets worse as z get's larger, as it has more scope to generate overlapping numbers.

Now, I'm sure there's some really awesome mathamtical forumal you could use, but I'm to lazy (and dumb) for that, instead, I'd use a Set of some kind to generate a random series of 25 numbers. This will ensure that each value is unique

public static void display1(int[][] card) {

    // Create the set
    Set<Integer> numbers = new HashSet<>(5 * 5);
    // Keep looping until we get 25 numbers
    while (numbers.size() < 5 * 5) {
        // Generate a random number
        numbers.add((int)Math.round(Math.random() * 100));
    }
    // This is just because I'm lazy...
    List<Number> listOfNumbers = new ArrayList<>(numbers);
    for (int i = 0; i < 5; i++) {

        for (int j = 0; j < 5; j++) {
            // Assign the value to the array...
            card[i][j] = (int)listOfNumbers.remove(0);
        }

    }

    // Add just for printing...you could do this in the previous loop
    // but I just wanted to keep it clean...
    for (int i = 0; i < card.length; i++) {

        for (int j = 0; j < card[i].length; j++) {
            System.out.printf("|%3d", card[i][j]);
        }
        System.out.println("|");

    }
}

Which will print something like...

|  0|  2| 71|  9| 74|
| 16| 22| 87| 24| 28|
| 93| 30| 33| 40| 41|
| 42| 49| 50| 51| 52|
| 55| 56| 59| 60| 63|

Now, if you aren't to attached to the array, you can use something like...

int index = (row * 5 + col);

to calculate the index offset into the List for a given row/col

for (int i = 0; i < card.length; i++) {
    for (int j = 0; j < card[i].length; j++) {
        int index = (i * 5 + j);
        System.out.printf("|%3d", listOfNumbers.get(index));
    }
    System.out.println("|");
}

Answer 2

Your problem seems to be you are only checking the previous number.

You need to loop through all of the numbers in the current section like this:

boolean numberFound = false;
while(!numberFound) {
  int number1 = (int) (Math.random() * z) + v;

  if(!checkNumber(number1, card, j)) break;

  card [i][j]=number1;
  System.out.print("|" + card[i][j]);
}

public static boolean checkNumber(int number, int[][] card, int j) {
  for(int a = 0; a <= j; a++) {
    if(card[i][a] == number) return false;
  }

  return true;
}