对如何为数组中的每列生成唯一随机数感到困惑

Question

I'm writing a program to create a bingo game for a class assignment, however I'm a little stuck on how to have a different numbers for each column in the 5x5 array. The code I have now is creating random numbers for the array, however some runs have the same numbers in a column. Any help would be greatly appreciated.

Below is some coding for the first two columns.

public static void newCard() {
        System.out.println("B" + "  " + "I" + "  " + "N" + "  " + "G" 
            + "  " + "O");
        int card [][] = new int[5][5];
        for (int i = 0; i < card.length; i++) {
            for (int j = 0; j < card[i].length; j++) { 
                    card[i][0] = (int)(Math.random() * 15 + 1);
                     if (card[i][0] == card[i][j]) {
                    card[i][0] = (int)(Math.random() * 15 + 1);
            card[i][1] = (int)(16 + Math.random() * 15);
                 if (card[i][1] == card[i][j]) {
                card[i][1] = (int)(16 + Math.random() * 15);
                    }
//New Code 
public static void main(String[] args) {
        int[][] card = newCard();
        System.out.println("B  I  N  G  O");
        for (int i = 0; i < card.length; i++) {
            for (int j = 0; j < card[i].length; j++) {
                System.out.printf("%2d ", card[j][i]);
            }
            System.out.println();
        }
        Scanner input = new Scanner(System.in);
        while (calledCard()) {
        System.out.println("Enter the called number: ");
        int number = input.nextInt();
        }
    }
public void calledCard(int number) {
        for(int i = 0; i <= 4; i++) {
            for(int j = 0; j <= 4; j++) {
                if(newCard()[i][j]==number) {
                    newCard()[i][j] = 0;
                }  else  {
                    continue;
                }
            }
        }

    }
The results I get are allowing each column to have some of the same numbers shown.

Answer 1

INFO:

A typical Bingo game utilizes the numbers 1 through 75. The five columns of the card are labeled 'B', 'I', 'N', 'G', and 'O' from left to right. The center space is usually marked "Free" or "Free Space", and is considered automatically filled. The range of printed numbers that can appear on the card is normally restricted by column, with the 'B' column only containing numbers between 1 and 15 inclusive, the 'I' column containing only 16 through 30, 'N' containing 31 through 45, 'G' containing 46 through 60, and 'O' containing 61 through 75.

you can use Collections.shuffle to randomize each List, here is how to use it:

     public static void newCard() {
        List<List<Integer>> nums = new ArrayList<>();
        int k=1;
        for (int i = 0; i <5; i++) {
            nums.add(new ArrayList<>());
            for(int j=0; j<15; j++){
                nums.get(i).add(k++);
            }
//            System.out.println(nums.get(i));
        }


        System.out.println("B" + "  " + "I" + "  " + "N" + "  " + "G"
                + "  " + "O");
        int card [][] = new int[5][5];
        for (int i = 0; i < card.length; i++) {
            Collections.shuffle(nums.get(i));
        }

        for (int i = 0; i < card.length; i++) {
            for (int j = 0; j < card[i].length; j++) {
                card[i][j] = nums.get(j).get(i);
                //System.out.print(card[i][j]+" ");
            }
            //System.out.println("");
        }
//        System.out.println(card);
    }

Answer 2

Since there is a valid range of values for each column (1-15 for B, 16-30 for I, 31-45 for N, 46-60 for G, and 61-75 for O), you can create a list containing the valid range, randomly shuffle it, and then pick the first five values from the list to fill the bingo card column.

Here is code to generate an array with values on the range [begin, end]:

public static int[] rangeClosed(int beginInclusive, int endInclusive) {
    if (beginInclusive > endInclusive) {
        throw new IllegalArgumentException("Begin must be less than or equal to end for range.");
    }
    int[] range = new int[endInclusive - beginInclusive + 1];
    for (int i = 0; i < range.length; i++) {
        range[i] = beginInclusive + i;
    }
    return range;
}

Here is code to swap two values in an array:

public static void swap(int[] array, int index1, int index2) {
    if (index1 < 0 || index1 >= array.length) {
        throw new IllegalArgumentException("Swap index one is out of bounds for the given array.");
    } else if (index2 < 0 || index2 >= array.length) {
        throw new IllegalArgumentException("Swap index two is out of bounds for the given array.");
    }
    int tmp = array[index1];
    array[index1] = array[index2];
    array[index2] = tmp;
}

Here is code to randomly shuffle an array by iterating through the array and randomly swapping each index with another:

public static void shuffle(int[] array) {
    Random rand = new Random();
    for (int i = 0; i < array.length; i++) {
        swap(array, i, rand.nextInt(array.length));
    }
}

Finally, here is the code to randomly generate the bingo card along with a main function to display it:

public static int[][] randomBingoCard() {
    int bingoRange = 15;
    int bingoCardSize = 5;
    int[][] card = new int[bingoCardSize][bingoCardSize];
    for (int i = 0; i < card.length; i++) {
        int[] columnRange = rangeClosed(i * bingoRange + 1, i * bingoRange + bingoRange); 
        shuffle(columnRange);
        for (int j = 0; j < card[i].length; j++) {
            card[i][j] = columnRange[j];
        }
    }
    return card;
}

public static void main(String[] args) {
    int[][] card = randomBingoCard();
    System.out.println("B  I  N  G  O");
    for (int i = 0; i < card.length; i++) {
        for (int j = 0; j < card[i].length; j++) {
            System.out.printf("%2d ", card[j][i]);
        }
        System.out.println();
    }
}

EDIT:

For your new question to fill in the card, I have included 3 new functions along with an updated main. One function to govern the loop by checking to see if all the numbers have been called, one to mark a number when called, and one function to print out the current card.

public static boolean allNumbersMarked(int[][] card) {
    for(int i = 0; i < card.length; i++) {
        for(int j = 0; j < card[i].length; j++) {
            if(card[i][j] != 0) {
                return false;
            }
        }
    }
    return true;
}

public static void markNumber(int[][] card, int number) {
    for(int i = 0; i < card.length; i++) {
        for(int j = 0; j < card[i].length; j++) {
            if(card[i][j] == number) {
                card[i][j] = 0;
            }
        }
    }
}

public static void printCard(int[][] card) {
    System.out.println("B  I  N  G  O");
    for (int i = 0; i < card.length; i++) {
        for (int j = 0; j < card[i].length; j++) {
            System.out.printf("%2d ", card[j][i]);
        }
        System.out.println();
    }
}

public static void main(String[] args) {
    int[][] card = randomBingoCard();
    printCard(card);
    Scanner input = new Scanner(System.in);
    while (!allNumbersCalled(card)) {
        System.out.println("Enter the called number: ");
        int number = input.nextInt();
        markNumber(card, number);
        printCard(card);
    }
    input.close();
}

Due to the new methods that are being added it makes sense to make a BingoCard object that does this for you. Before when you just wanted a card, a simple static function and main were sufficient, however now it would be worth while to make this program Object Oriented.