private TreeNode MiniMax(Board board, Double depth, Double alpha, Double beta, Boolean maximizer)
{
if(depth == 0)
{
return GetLeafNode(board, maximizer);
}
var pieces = board.GetPiecesForPlayer(board.PlayerTurn);
var bestScore = maximizer ? _minScore : _maxScore;
var bestMove = default(Move);
var moves = pieces.SelectMany(x => x.GetPossibleMoves(board));
if (!moves.Any())
{
if (board.PlayerHasCheck(board.PlayerTurn))
{
return new TreeNode(null, maximizer ? _maxScore : _minScore);
}
}
foreach (var mv in moves)
{
var newBoard = board.Copy();
newBoard.MakeMove(mv);
var newNode = MiniMax(newBoard, depth - 1, alpha, beta, !maximizer);
if (maximizer)
{
if(newNode.Score > bestScore)
{
bestScore = newNode.Score;
bestMove = mv;
}
alpha = Math.Max(alpha, bestScore);
if(beta <= alpha)
{
return new TreeNode(bestMove, bestScore);
}
}
else
{
if(newNode.Score < bestScore)
{
bestScore = newNode.Score;
bestMove = mv;
}
beta = Math.Min(beta, bestScore);
if(beta <= alpha)
{
return new TreeNode(bestMove, bestScore);
}
}
}
return new TreeNode(bestMove, bestScore);
}
public Move GetNextMove(Board board)
{
var allMoves = new List<Move>();
var pcs = board.GetPiecesForPlayer(board.PlayerTurn);
foreach(var pc in pcs)
{
var moves = pc.GetPossibleMoves(board);
allMoves.AddRange(moves);
}
var randomIndex = new Random().Next(allMoves.Count);
return allMoves[randomIndex];
}
public double Evaluate(Board board)
{
Double score = 0;
var playerPieces = board.GetPiecesForPlayer(board.PlayerTurn);
var opposingPieces = board.GetPiecesForPlayer(board.OpposingPlayer());
score = GetScore(playerPieces, board);
score -= GetScore(opposingPieces, board);
//score = 200 * (CountPiecesByType(playerPieces, PieceType.King) - CountPiecesByType(opposingPieces, PieceType.King));
//score += 9 * (CountPiecesByType(playerPieces, PieceType.Queen) - CountPiecesByType(opposingPieces, PieceType.Queen));
//score += 5 * (CountPiecesByType(playerPieces, PieceType.Rook) - CountPiecesByType(opposingPieces, PieceType.Rook));
//score += 3 * ((CountPiecesByType(playerPieces, PieceType.Bishop) - CountPiecesByType(opposingPieces, PieceType.Bishop)) +
// (CountPiecesByType(playerPieces, PieceType.Knight) - CountPiecesByType(opposingPieces, PieceType.Knight)));
//score += 1 * (CountPiecesByType(playerPieces, PieceType.Pawn) - (CountPiecesByType(opposingPieces, PieceType.Pawn)));
//score -= .5 * ((DoubledPawns(playerPieces) - DoubledPawns(opposingPieces)) +
// (BlockedPawns(playerPieces) - BlockedPawns(opposingPieces)) +
// (IsolatedPawns(playerPieces) - IsolatedPawns(opposingPieces)));
//score += .1 * (CountMoves(board, playerPieces) - CountMoves(board, opposingPieces));
return score;
}
