使用C＃将Minimax算法实现到井字游戏

如何解决使用C＃将Minimax算法实现到井字游戏

我正在尝试将minimax算法实施到井字游戏中，在该游戏中计算机将基于minimax算法播放最佳动作。我已经编写了整个算法，但是AI产生了奇怪且看似随机的动作。例如，当井字游戏板 的布局如图所示：

' ' 'o' 'x'
' ' 'o' ' '
'x' ' ' ' '

然后，Minimax算法选择第一个位置，这显然不是最佳选择：

'o' 'o' 'x'
' ' 'o' ' '
'x' ' ' ' '

这是我的代码：

namespace MinimaxAlg
{
    class Program
    {
        static void Main(string[] args)
        {
            char[,] board = { { '-','o','x'},{ '-','-'},{ 'x','-','-'} };

            int bestscore = int.MinValue;
            int moveI = -1;
            int moveJ = -1;

            for (var i = 0; i < 3; i++)
            {
                for (var j = 0; j < 3; j++)
                {
                    if (board[i,j] == '-')
                    {
                        board[i,j] = 'o';
                        var score = Minimax(board,'o');
                        board[i,j] = '-';

                        Console.WriteLine("score: " + score);
                        Console.WriteLine("Bestscore: " + bestscore);


                        if (score > bestscore)
                        {
                            bestscore = score;
                            moveI = i;
                            moveJ = j;
                        }
                    }
                }
            }
            board[moveI,moveJ] = 'p';

            foreach (var i in board)
            {
                Console.WriteLine(i);
            }
        }

        static int Minimax(char[,] board,char forWho)
        {
            if (CheckWhoWins(board,forWho))
            {
                return 1;
            }

            if (forWho == 'o')
            {
                var bestscore = int.MinValue;
                for (var i = 0; i < 3; i++)
                {
                    for (var j = 0; j < 3; j++)
                    {
                        if (board[i,j] == '-')
                        {
                            board[i,j] = forWho;
                            var score = Minimax(board,'x');
                            board[i,j] = '-';

                            bestscore = Math.Max(bestscore,score);
                        }
                    }
                }
                return bestscore;
            }
            else
            {
                var bestscore = int.MaxValue;
                for (var i = 0; i < 3; i++)
                {
                    for (var j = 0; j < 3; j++)
                    {
                        if (board[i,'o');
                            board[i,j] = '-';

                            bestscore = Math.Min(bestscore,score);
                        }
                    }
                }
                return bestscore;
            }
        }


        static bool CheckWhoWins(char[,char forWho)
        {
            if ((board[0,0] == forWho && board[0,1] == forWho && board[0,2] == forWho) || (board[1,0] == forWho && board[1,1] == forWho && board[1,2] == forWho) ||
                (board[2,0] == forWho && board[2,1] == forWho && board[2,2] == forWho) || (board[0,0] == forWho) ||
                (board[0,1] == forWho) || (board[0,2] == forWho && board[1,2] == forWho && board[2,2] == forWho) ||
                (board[0,0] == forWho) || (board[0,0] == forWho))
                return true;
            else
                return false;
        }
    }
}

如果任何人对可能出什么问题有任何想法，将不胜感激。

解决方法

您的代码中存在三个问题。

首先，一个简单的错字。您获胜的条件之一是board[0,0] == forWho && board[1,1] == forWho && board[0,0] == forWho。显然，最后一个应该是board[2,2]。

第二，您马上给o两笔。这些行显示出来：

board[i,j] = 'o';
var score = Minimax(board,'o');

第二行应为var score = Minimax(board,'x');。

最后，user3386109钉住了它。您要给长游戏和短游戏赋予相同的分数。

如果我们改变计分系统，以便为最少的动作提供更大的分数，那么它就可以正常工作。

static int CheckWhoWins(char[,] board,char forWho)
{
    if ((board[0,0] == forWho && board[0,2] == forWho)
        || (board[1,1] == forWho && board[1,2] == forWho)
        || (board[2,0] == forWho && board[2,1] == forWho && board[2,2] == forWho)
        || (board[0,0] == forWho)
        || (board[0,1] == forWho)
        || (board[0,2] == forWho && board[1,2] == forWho && board[2,0] == forWho))
    {
        var score = 1;
        for (var i = 0; i < 3; i++)
        {
            for (var j = 0; j < 3; j++)
            {
                if (board[i,j] == '-')
                {
                    score++;
                }
            }
        }
        return score;
    }
    else
        return 0;
}

Minimax（应该只是MinMax）现在是：

static int Minimax(char[,char forWho)
{
    var score = CheckWhoWins(board,forWho);
    if (score != 0)
    {
        return score;
    }

    if (forWho == 'o')
    {
        var bestScore = int.MinValue;
        for (var i = 0; i < 3; i++)
        {
            for (var j = 0; j < 3; j++)
            {
                if (board[i,j] == '-')
                {
                    board[i,j] = forWho;
                    var currentScore = Minimax(board,'x');
                    board[i,j] = '-';

                    bestScore = Math.Max(bestScore,currentScore);
                }
            }
        }
        return bestScore;
    }
    else
    {
        var bestScore = int.MaxValue;
        for (var i = 0; i < 3; i++)
        {
            for (var j = 0; j < 3; j++)
            {
                if (board[i,'o');
                    board[i,j] = '-';

                    bestScore = Math.Min(bestScore,currentScore);
                }
            }
        }
        return bestScore;
    }
}

运行此命令可获得以下结果：

---

在我看来，关于奖励积分，这是Minimax的一个更好的版本：

static int Minimax(char[,forWho);
    if (score != 0)
    {
        return score;
    }

    var bestScore = forWho == 'o' ? int.MinValue : int.MaxValue;

    int CalcBest(int x,int y) => (forWho == 'o' ? x > y : y > x) ? x : y;
    
    for (var i = 0; i < 3; i++)
    {
        for (var j = 0; j < 3; j++)
        {
            if (board[i,j] == '-')
            {
                board[i,j] = forWho;
                var currentScore = Minimax(board,forWho == 'o' ? 'x' : 'o');
                board[i,j] = '-';

                bestScore = CalcBest(bestScore,currentScore);
            }
        }
    }
    return bestScore;
}