C#中的数独算法

using System;

class SudokuSolver
{
    private int[,] sudoku;

    public SudokuSolver(int[,] sudoku)
    {
        this.sudoku = sudoku;
    }

    public bool Solve()
    {
        return Solve(0, 0);
    }

    private bool Solve(int row, int col)
    {
        if (row == 9)
        {
            return true;
        }

        int nextRow = row;
        int nextCol = col + 1;

        if (nextCol == 9)
        {
            nextRow++;
            nextCol = 0;
        }

        if (sudoku[row, col] != 0)
        {
            return Solve(nextRow, nextCol);
        }

        for (int num = 1; num <= 9; num++)
        {
            if (IsValid(row, col, num))
            {
                sudoku[row, col] = num;

                if (Solve(nextRow, nextCol))
                {
                    return true;
                }

                sudoku[row, col] = 0;
            }
        }

        return false;
    }

    private bool IsValid(int row, int col, int num)
    {
        for (int i = 0; i < 9; i++)
        {
            if (sudoku[row, i] == num || sudoku[i, col] == num)
            {
                return false;
            }
        }

        int boxRow = row / 3 * 3;
        int boxCol = col / 3 * 3;

        for (int i = 0; i < 3; i++)
        {
            for (int j = 0; j < 3; j++)
            {
                if (sudoku[boxRow + i, boxCol + j] == num)
                {
                    return false;
                }
            }
        }

        return true;
    }
}