public override ushort Move(TicTacToeBoard currentBoard)
{
ushort chosenMove = 0;
do
{
// call the method used to determine the move
chosenMove = this.moveMethod(currentBoard, this.Token);
} while (currentBoard.At(chosenMove));
return(chosenMove);
}
public static ushort MinMaxMove(TicTacToeBoard board, Piece.PieceValue token)
{
// computer always plays the center square if it is available
if (!board.At(4))
{
return(4);
}
// computer's 2nd move should be a corner if computer went first
// computer's 1st move should be a corner if the center is taken
// really not the best strategy
if ((board.Moves == 1 && board.At(4)) || board.Moves == 2)
{
return((TicTacToeBoard.Corners)[Computer.randNum.Next(0, TicTacToeBoard.Corners.Length - 1)]);
}
// start with recommended move
ushort aMove = 4;
// use MinMax strategy to find the next move
MoveStrategy strategy = Computer.LookAhead(new Piece(token), new TicTacToeBoard(board), ref aMove);
return(aMove);
}
public override ushort Move(TicTacToeBoard currentBoard)
{
// computer's algorithm will modify the board so create a copy to work on
// TicTacToeBoard tempBoard = new TicTacToeBoard(currentBoard);
// call the method used to determine the move
ushort chosenMove = this.moveMethod(currentBoard, this.Token);
while (currentBoard.At(chosenMove))
{
chosenMove = this.moveMethod(currentBoard, this.Token);
}
return(chosenMove);
}
/// <summary>Draws the current board for a command line interface.</summary>
private void DrawBoard()
{
byte i = 0; // iterator
// iterate through the board
for (i = 0; i < theBoard.Length; ++i)
{
if (theBoard.At(i))
{
switch (theBoard.GetAt(i).Value)
{
case Piece.PieceValue.X:
Console.Write("X ");
break;
case Piece.PieceValue.O:
Console.Write("O ");
break;
default:
// some kind of error has occured
throw new System.Exception();
} // end switch
}
else
{
Console.Write("{0} ", i);
}
// start a new line after mDim squares
if (i % theBoard.Dimension == theBoard.Dimension - 1)
{
Console.WriteLine();
}
} // end for loop
}
protected static MoveStrategy LookAhead(Piece inPiece, TicTacToeBoard inBoard, ref ushort bestMove)
{
// unused dummy value to seend the algorithm
ushort aDummy = 0;
// temporary strategy
MoveStrategy aResponse;
// the strategy to return
MoveStrategy outValue = (inPiece.Value == Piece.PieceValue.X) ? MoveStrategy.OWin - 1 : MoveStrategy.XWin + 1;
// first check to see if the game is a draw
if (inBoard.Full())
{
outValue = MoveStrategy.Draw;
}
// return any move that results in an immediate win
else if (Computer.ImmediateWin(inPiece, inBoard, ref bestMove))
{
outValue = (inPiece.Value == Piece.PieceValue.X) ? MoveStrategy.XWin : MoveStrategy.OWin;
}
// return any move that will result in blocking the other player from an immediate win on his next turn
else if (Computer.ImmediateBlock(inPiece, inBoard, ref bestMove))
{
outValue = (inPiece.Value == Piece.PieceValue.X) ? MoveStrategy.XBlock : MoveStrategy.OBlock;
}
// no immediate wins so look for a promising move
else
{
for (ushort i = 0; i < inBoard.Length; ++i)
{
if (!inBoard.At(i))
{
inBoard.Place(inPiece, i);
// swap pieces and go down a move
Piece aPiece = (inPiece.Value == Piece.PieceValue.X) ? new Piece(Piece.PieceValue.O) : new Piece(Piece.PieceValue.X);
// call look ahead recursively with a copy of the board each time
aResponse = LookAhead(aPiece, new TicTacToeBoard(inBoard), ref aDummy);
// determine the best move
switch (inPiece.Value)
{
case Piece.PieceValue.X:
if (aResponse > outValue)
{
outValue = aResponse;
bestMove = i;
}
break;
case Piece.PieceValue.O:
if (aResponse < outValue)
{
outValue = aResponse;
bestMove = i;
}
break;
default:
break;
} // end switch
} // end if
} // end for loop
} // end else
// return the best move strategy
return(outValue);
}
