数独小算法，测试通过(Java)

class SudokuMatrix {

    private int[][] matrix = new int[][] {            {0, 5, 0, 6, 0, 1, 0, 0, 0},            {0, 0, 7, 0, 9, 0, 0, 2, 0},            {3, 0, 0, 0, 0, 4, 0, 0, 1},            {9, 0, 0, 0, 0, 0, 1, 3, 0},            {0, 0, 8, 0, 5, 0, 7, 0, 0},            {0, 2, 6, 0, 0, 0, 0, 0, 8},            {7, 0, 0, 9, 0, 0, 0, 0, 5},            {0, 9, 0, 0, 4, 0, 3, 0, 0},            {0, 0, 0, 2, 0, 8, 0, 1, 0},    };

    public void run(){        calc();    }

    private void calc() {

        int[] coordinate = getNextData();        int m = coordinate[0];        int n = coordinate[1];

        for (int k = 1; k <= 9; k++) {            if(checkNumber(m,n,k)) {                matrix[m][n] = k;

                //System.out.println( m + "," + n + " with " + k );

                if ( getNextData() == null ) {                    print(matrix);                }                else {                    calc();                }            }

        }

        matrix[m][n] = 0;    }

    private int[] getNextData(){

        for (int row = 0; row < 9; row++) {            for (int col = 0; col < 9; col++) {                if (matrix[row][col] == 0) {                    int[] coordinateOfEmptySquare = {row, col};                    return coordinateOfEmptySquare;                }            }        }

        return null;    }

    private boolean checkNumber(int row, int col, int n) {        for (int i = 0; i < 9; i++) {            if (matrix[row][i] == n || matrix[i][col] == n) {                return false;            }        }

        int[] leftTop = {row - (row % 3), col - (col % 3)};

        for (int r = leftTop[0]; r <= leftTop[0] + 2; r++) {            for (int c = leftTop[1]; c <= leftTop[1] + 2; c++) {                if (matrix[r][c] == n) {                    return false;                }            }        }

        return true;    }

    public void print(int[][] grid) {        for (int i = 0; i < 9; i++) {            for (int j = 0; j < 9; j++) {                System.out.print(grid[i][j] + " ");            }            System.out.println();        }        System.out.println();    }

}