试图在Tic Tac Toe中使用Negamax时出现堆栈溢出

Question

如果这是重新发布的话我提前道歉，但我已经阅读了有关该主题的其他帖子，我仍然无法弄清楚该怎么做。我试图在ruby tic tac toe游戏中实现Negamax，我在第55行遇到了堆栈溢出错误。我在Negamax上阅读了很多帖子和文章，我仍然无法让它工作。

这个文件还不是一个更大的程序的一部分，我只是想通过一个董事会，看看它是否会采取行动。

class Negamax

    attr_accessor :board, :mark, :depth, :winning_routes

    def initialize
        @board = ["X","2","3","4","5","6","7","8","9"]
        @mark = "O"
        @depth = 1
        @winning_routes = [[0,1,2],[3,4,5],[6,7,8],[0,3,6],[1,4,7],[2,5,8],[0,4,8],[2,4,6]]
    end

    def negamax(board, mark, depth)
        if winner?(mark) || isboardfull?(board)
            return game_result(mark)
        else 
            max = -1.0/0
            mark == "O" ? opponent = "X" : "O"
            available_moves.each do |space|
                board[space] = mark
                score = -negamax(board, opponent, depth + 1)
                board[space] = "#{space + 1}"
                if score > max
                    max = score
                    best_move = space if depth == 1
                    board[best_move] = mark
                end
            end
            return max
        end
    end

    def available_moves()
        board.each_index.select { |s| board[s] != "X" && board[s] != "O"}
    end

    def isboardfull?(board)
        boardtos = board.join(",")
        boardtos =~ /\d/ ? false : true
    end

    def game_result(mark)
        if winner?(mark)
            return 1
        elsif winner?(mark == "O" ? "X" : "O")
            return -1
        else 
            return 0
        end
    end

    def winner?(mark)
        result = false
        marker = mark
        winning_routes.each do |group|
            if board[group[0]] == marker && board[group[1]] == marker && board[group[2]] == marker
                result = true
            end
        end
        result
    end
end

game = Negamax.new()
game.negamax(game.board, game.mark, game.depth)
print game.board