java - 用范围内的随机数字填充数组

Question

我正在编写一个数独棋盘游戏生成器。我的代码如下所示:

/**
 * Created by szubansky on 3/9/16.
 */

public class SudokuBoard {

    static int N = 9;
    static int[][] grid = new int[N][N];

    static void printGrid()
    {
        for (int row = 0; row < N; row++)
        {
            for (int col = 0; col < N; col++) {
                System.out.printf("%5d", grid[row][col]);
            }
            System.out.println("\n");
        }
    }

    private static boolean checkRow(int row, int num)
    {
        for( int col = 0; col < 9; col++ )
            if(grid[row][col] == num)
                return false;

        return true;
    }

    private static boolean checkCol(int col, int num)
    {
        for( int row = 0; row < 9; row++ )
            if(grid[row][col] == num)
                return false;

        return true;
    }

    private static boolean checkBox(int row, int col, int num)
    {
        row = (row / 3) * 3;
        col = (col / 3) * 3;

        for(int r = 0; r < 3; r++)
            for(int c = 0; c < 3; c++)
                if(grid[row+r][col+c] == num)
                    return false;

        return true;
    }

    public static boolean fillBoard(int row, int col, int[][] grid)
    {
        if(row==9) {
            row = 0;
            if (++col == 9)
                return true;
        }

        if(grid[row][col] != 0)
            return fillBoard(row+1, col, grid);
        for(int num=1 + (int)(Math.random() * ((9 - 1) + 1)); num<=9; num++)
        {
            if(checkRow(row,num) && checkCol(col,num) && checkBox(row,col,num)){
                grid[row][col] = num;
                if(fillBoard(row+1, col, grid))
                    return true;
            }
        }
        grid[row][col] = 0;
        return false;
    }

    static public void main(String[] args){
        fillBoard(0, 0, grid);
        printGrid();
    }
}

问题是在 fillBoard 回溯算法中生成数字它基本上到处都是 0当我将 for 循环中的 num 范围更改为 10 时，它进行得很顺利，但我的数字需要低于 9我还可以将回溯 fillBoard 的开头更改为 row==8 和 col==8 并用随机数正确填充它，最后一行和最后一列为“0 ”。如何生成 1 到 9 的随机数并填满我的所有网格？

Answer 1

试试这个:

public static void main(String[] args) {
    int[][] grid = new int[9][9];
    randomFillGrid(grid, 1, 10);
    for (int[] row : grid) {
        System.out.println(Arrays.toString(row));
    }
}

static void randomFillGrid(int[][] grid, int randomNumberOrigin, int randomNumberBound) {
    PrimitiveIterator.OfInt iterator = ThreadLocalRandom.current()
            .ints(randomNumberOrigin, randomNumberBound)
            .iterator();
    for (int[] row : grid) {
        for (int i = 0; i < row.length; i++) {
            row[i] = iterator.nextInt();
        }
    }
}

编辑:

如果你想生成一个数独网格即

the same single integer may not appear twice in the same row, column or in any of the nine 3×3 subregions of the 9x9 playing board.

import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

/**
 * @author FaNaJ
 */
public class SudokuGenerator {

    private static final int N = 9;
    private static final int S_N = 3;

    public static int[][] generateSudokuGrid() {
        int[][] grid = new int[N][N];
        int[] row = {1, 2, 3, 4, 5, 6, 7, 8, 9};

        for (int y = 0; y < N; y++) {
            int attempts = 0;

            do {
                if (++attempts > 1000000) { // Oops! I know (sometimes :) it's not a good algorithm...
                    return generateSudokuGrid();
                }
                shuffleArray(row);
            } while (!isAllowed(grid, y, row));

            System.arraycopy(row, 0, grid[y], 0, N);
        }

        return grid;
    }

    static boolean isAllowed(int[][] grid, int y, int[] row) {
        // check columns
        for (int i = 0; i < y; i++) {

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

                if (grid[i][j] == row[j]) {
                    return false;
                }

            }

        }

        // check sub grids
        int startY = (y / S_N) * S_N;

        for (int x = 0; x < N; x++) {
            int startX = (x / S_N) * S_N;
            for (int j = startX; j < startX + S_N; j++) {
                if (j != x) {

                    for (int i = startY; i < y; i++) {

                        if (grid[i][j] == row[x]) {
                            return false;
                        }

                    }

                }
            }
        }

        return true;
    }

    static void shuffleArray(int[] array) {
        Random random = ThreadLocalRandom.current();
        for (int i = N; i > 1; i--) {
            swap(array, i - 1, random.nextInt(i));
        }
    }

    static void swap(int[] array, int i, int j) {
        int tmp = array[i];
        array[i] = array[j];
        array[j] = tmp;
    }

    public static void main(String[] args) {
        int[][] grid = generateSudokuGrid();
        for (int[] row : grid) {
            System.out.println(Arrays.toString(row));
        }
    }

}

输出:

[3, 4, 6, 9, 1, 2, 7, 8, 5]
[9, 7, 2, 3, 8, 5, 4, 1, 6]
[5, 8, 1, 6, 7, 4, 3, 2, 9]
[7, 6, 3, 8, 2, 9, 1, 5, 4]
[4, 9, 5, 1, 6, 7, 2, 3, 8]
[2, 1, 8, 4, 5, 3, 6, 9, 7]
[6, 2, 4, 5, 9, 1, 8, 7, 3]
[8, 5, 7, 2, 3, 6, 9, 4, 1]
[1, 3, 9, 7, 4, 8, 5, 6, 2]