public IEnumerable <IPositional> Search(Game game, int maxTile = 2, int blankTolerance = 1)
{
if (game is null)
{
throw new ArgumentNullException(nameof(game));
}
if (maxTile < 0)
{
throw new ArgumentException(nameof(maxTile));
}
if (blankTolerance < 0)
{
throw new ArgumentException(nameof(blankTolerance));
}
// Get all the placed tiles to determine all the correct playable tiles
IReadOnlyList <Tile> placedTiles = game.History;
// Get all the playable tiles using a HashSet where only distinct tiles
// are added
var playableTiles = new HashSet <Tile>();
foreach (Tile tile in placedTiles)
{
// Loop all 4 Orientation enumeration
Orientations[] orientations = new[]
{
Orientations.Horizontal,
Orientations.Vertical,
Orientations.Diagonal,
Orientations.RvDiagonal
};
foreach (Orientations orientation in orientations)
{
// Retrieve line of each orientation within 2-tile range where the
// tiles are empty
foreach (Tile t in
OrientedlLine.FromBoard(
game.Board,
tile.X,
tile.Y,
(Piece)Pieces.None,
orientation,
maxTile: maxTile,
blankTolerance: blankTolerance)
.GetSameTiles())
{
playableTiles.Add(t);
}
}
}
return(playableTiles);
}
/// <summary>
/// Evaluates a <paramref name="game"/>'s state at
/// <paramref name="positional"/> for <paramref name="piece"/>.
/// </summary>
/// <param name="game">the <see cref="Game"/> to be evaluated.</param>
/// <param name="positional">the <see cref="IPositional"/> to evaluate.</param>
/// <param name="piece">the <see cref="Piece"/> to evaluate for.</param>
/// <returns>
/// A non-negative number representing the probability of winning the game
/// at <paramref name="positional"/>. The only negative number
/// <see cref="double.MinValue"/> is returned when the
/// <paramref name="game"/> is lost but the winner is not
/// <paramref name="piece"/>. If the <paramref name="piece"/> wins the
/// <paramref name="game"/>, returns <see cref="double.MaxValue"/>
/// </returns>
/// <exception cref="ArgumentException"></exception>
/// <exception cref="ArgumentNullException"></exception>
public double Evaluate(Game game, IPositional positional, Piece piece)
{
if (game is null)
{
throw new ArgumentNullException(nameof(game));
}
if (positional is null)
{
throw new ArgumentNullException(nameof(positional));
}
if (piece == Pieces.None)
{
throw new ArgumentException($"{nameof(piece)} must not be {Pieces.None}");
}
var point = 0.0;
// If game is over the point should be high enough so that this node is
// more likely to get noticed
if (game.IsOver)
{
if (game.Manager.PreviousPlayer.Piece == piece)
{
point = double.MaxValue;
}
else
{
point = double.MinValue;
}
}
// Otherwise evaluate the point matching lines and other information
else
{
// Retrieve line group of each orientation to fully evaluate a tile
Orientations[] orientations = new[]
{
Orientations.Horizontal,
Orientations.Vertical,
Orientations.Diagonal,
Orientations.RvDiagonal
};
foreach (Orientations orientation in orientations)
{
// Get line within 5-tile range
var line =
OrientedlLine.FromBoard(
game.Board,
positional.X,
positional.Y,
piece,
orientation,
maxTile: Game.WINPIECES,
blankTolerance: 1);
// Calculate points
var sameTilesCount = line.SameTileCount;
var blockTilesCount = line.BlockTilesCount;
// When the line is not blocked
if (blockTilesCount == 0)
{
// If the line chain has more tiles than win pieces, then this tile
// is less worth.
if (sameTilesCount + 1 >= Game.WINPIECES)
{
point += sameTilesCount;
}
// Otherwise
else
{
// Calculate point using Geometric series of 2.0 so that the more
// chain it has, the more valuable the line
var _point =
1.0 * (1.0 - Math.Pow(2.0, sameTilesCount)) / (1.0 - 2.0);
if (_point < 0)
{
throw new Exception();
}
// Finally the point is added with the power of itself
point += Math.Pow(_point, line.IsChained ? 2.0 : 1.5);
}
}
// When the line is partially blocked, only add the point which equals
// to the same count
else if (blockTilesCount == 1)
{
point += sameTilesCount;
}
// Otherwise, add no point.
//point += (1.0 * (1.0 - Math.Pow(2.0, line.CountChainTiles())) / (1.0 - 2.0));
//point += 0.25 * line.CountBlankTiles();
//point -= 1.0 * line.BlockTileCount;
}
}
return(point);
}
