public Move GetBestMove(Board board)
{
int bestValue = int.MinValue;
Move bestMove = null;
List <Move> pseudoLegalMoves = MoveGeneration.GenerateAllMoves(board, Piece.black);
SortMoves(board, pseudoLegalMoves);
foreach (var move in pseudoLegalMoves)
{
board.MakeMove(move, true);
if (MoveGeneration.IsInCheck(board, Piece.black))
{
board.UnMakeMove(true);
continue;
}
int value = Minimax(board, depth, int.MinValue, int.MaxValue, false);
board.UnMakeMove(true);
if (value >= bestValue)
{
bestValue = value;
bestMove = move;
}
}
return(bestMove);
}
private int Minimax(Board board, int depth, int alpha, int beta, bool isMaximizingPlayer)
{
if (depth == 0)
{
return(Evaluate(board));
}
if (isMaximizingPlayer)
{
int bestValue = int.MinValue;
List <Move> pseudoLegalMoves = MoveGeneration.GenerateAllMoves(board, Piece.black);
SortMoves(board, pseudoLegalMoves);
foreach (var move in pseudoLegalMoves)
{
board.MakeMove(move, true);
if (MoveGeneration.IsInCheck(board, Piece.black))
{
board.UnMakeMove(true);
continue;
}
int value = Minimax(board, depth - 1, alpha, beta, false);
board.UnMakeMove(true);
bestValue = Math.Max(value, bestValue);
alpha = Math.Max(alpha, value);
if (beta <= alpha)
{
break;
}
}
return(bestValue);
}
else
{
int bestValue = int.MaxValue;
List <Move> pseudoLegalMoves = MoveGeneration.GenerateAllMoves(board, Piece.white);
SortMoves(board, pseudoLegalMoves);
foreach (var move in pseudoLegalMoves)
{
board.MakeMove(move, true);
if (MoveGeneration.IsInCheck(board, Piece.white))
{
board.UnMakeMove(true);
continue;
}
int value = Minimax(board, depth - 1, alpha, beta, true);
board.UnMakeMove(true);
bestValue = Math.Min(value, bestValue);
beta = Math.Min(beta, value);
if (beta <= alpha)
{
break;
}
}
return(bestValue);
}
}
