// MiniMax algorithm
private int MiniMaxAlgorithm(int depth, bool isMaximizing)
{
TicTacToeChecker ticTacToeChecker = new TicTacToeChecker();
// checking board state
if (ticTacToeChecker.CheckIfSymbolWon(TicTacToeSymbol.Circle, _boardBeforeMove))
{
return(10);
}
else if (ticTacToeChecker.CheckIfSymbolWon(TicTacToeSymbol.Cross, _boardBeforeMove))
{
return(-10);
}
else if (ticTacToeChecker.GameEnded(_boardBeforeMove))
{
return(0);
}
if (depth >= _maxDepth)
{
return(0);
}
if (isMaximizing) // circle should be the best
{
int bestScore = -int.MaxValue;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (_boardBeforeMove[i, j] == TicTacToeSymbol.Empty)
{
_boardBeforeMove[i, j] = TicTacToeSymbol.Circle;
int scoreMax = MiniMaxAlgorithm(depth + 1, false);
_boardBeforeMove[i, j] = TicTacToeSymbol.Empty;
bestScore = Math.Max(scoreMax, bestScore);
}
}
}
return(bestScore);
}
else // cross should be the worst
{
int bestScore = int.MaxValue;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (_boardBeforeMove[i, j] == TicTacToeSymbol.Empty)
{
_boardBeforeMove[i, j] = TicTacToeSymbol.Cross;
int scoreMin = MiniMaxAlgorithm(depth + 1, true);
_boardBeforeMove[i, j] = TicTacToeSymbol.Empty;
bestScore = Math.Min(scoreMin, bestScore);
}
}
}
return(bestScore);
}
}
