public double AlphaBeta(TicTacToeBoard oldBoard, double alpha, double beta, int player)
{
if (oldBoard.CheckForWin() != 0 || oldBoard.CheckForDraw())
{
return Score(oldBoard);
}
if (player == 1)
{
double val = -10000.0;
for (int i = 1; i <= 9; i++)
{
if (oldBoard.GetMove(i) == 0)
{
TicTacToeBoard newBoard = new TicTacToeBoard(oldBoard);
newBoard.MakeMove(i, player);
val = Math.Max(val, gamma * AlphaBeta(newBoard, alpha, beta, 2));
alpha = Math.Max(alpha, val);
if (beta <= alpha) break;
}
}
return alpha;
}
else
{
double val = 10000.0;
for (int i = 1; i <= 9; i++)
{
if (oldBoard.GetMove(i) == 0)
{
TicTacToeBoard newBoard = new TicTacToeBoard(oldBoard);
newBoard.MakeMove(i, player);
val = Math.Min(val, gamma * AlphaBeta(newBoard, alpha, beta, 1));
beta = Math.Min(val, beta);
if (beta <= alpha) break;
}
}
return beta;
}
}
public void TakeATurn(TicTacToeBoard board)
{
board.DisplayBoard();
bool validMove = false;
while (!validMove)
{
Console.WriteLine("Please make a move (1-9):");
int move;
if (Int32.TryParse(Console.ReadLine(), out move))
{
if (board.GetMove(move) == 0)
{
board.MakeMove(move, 2);
validMove = true;
}
else
{
Console.WriteLine("Invalid move. Please try again.");
}
}
else
{
Console.WriteLine("Invalid syntax. Please try again.");
}
}
}
public int GetBestMove(TicTacToeBoard board)
{
double max = -100000.0;
int bestMoveSoFar = 0;
for (int i = 1; i <= 9; i++)
{
if (board.GetMove(i) == 0)
{
TicTacToeBoard testBoard = new TicTacToeBoard(board);
testBoard.MakeMove(i, 1);
double moveScore = AlphaBeta(testBoard, -10000.0, 10000.0, 2);
if (moveScore > max)
{
max = moveScore;
bestMoveSoFar = i;
}
}
}
return bestMoveSoFar;
}
