private int minimaxScoreWithCache(char[,] board, char currentSymbol)
{
Tuple <bool, char> result = BoardUtils.ComputeGameResult(board, Engine.EMPTY_CHAR);
if (result.Item1)
{
// win
if (result.Item2 == Symbol)
{
return(10);
}
// loose
else if (result.Item2 != Engine.EMPTY_CHAR)
{
return(-10);
}
// draw
else
{
return(0);
}
}
List <int> scores = new List <int>();
foreach (var move in BoardUtils.GetAllLegalMoves(board, Engine.EMPTY_CHAR))
{
char[,] workingBoard = (char[, ])board.Clone();
workingBoard[move.Item1, move.Item2] = currentSymbol;
string key = GetCustomHash(workingBoard);
if (!cache.ContainsKey(key))
{
IPlayer opponent = PlayerManager.GetInstance().GetOpponent(currentSymbol);
int score = minimaxScoreWithCache(workingBoard, opponent.Symbol);
cache.Add(key, score);
}
scores.Add(cache[key]);
}
// if current player is our IA, we try to maximize the score,
// else minimize it
if (currentSymbol == Symbol)
{
return(scores.Max());
}
else
{
return(scores.Min());
}
}
internal override Tuple <int, int> AskNextMove(char[,] board)
{
Tuple <int, int> bestMove = null;
int bestScore = int.MinValue;
foreach (var move in BoardUtils.GetAllLegalMoves(board, Engine.EMPTY_CHAR))
{
char[,] workingBoard = (char[, ])board.Clone();
workingBoard[move.Item1, move.Item2] = Symbol;
IPlayer opponent = PlayerManager.GetInstance().GetOpponent(Symbol);
int currentScore = minimaxScoreWithCache(workingBoard, opponent.Symbol);
if (currentScore > bestScore)
{
bestScore = currentScore;
bestMove = new Tuple <int, int>(move.Item1, move.Item2);
}
}
return(bestMove);
}