/// <summary>
/// Execute Alpha - Beta Negemax search to find the next best cell.
/// </summary>
/// <returns>
/// The best cell and its score.
/// </returns>
/// <param name='board'>
/// The Game Board.
/// </param>
/// <param name='cell'>
/// The last taken <see cref="Yavalath.cell"/>.
/// </param>
/// <param name='height'>
/// The Height to which the search should be run until.
/// </param>
/// <param name='achievable'>
/// The Achievable Cell.
/// </param>
/// <param name='hope'>
/// Hope.
/// </param>
/// <param name='player'>
/// Player.
/// </param>
public static SearchResult ABNegamax(Board board, Cell cell, int height,
SearchResult achievable, SearchResult hope, int player)
{
var emptyCells = board.EmptyCells ();
if (height == 0 || emptyCells.Length == 0) {
return new SearchResult {
Score = Evaluation (board, cell, player),
Cell = cell,
Count = 1
};
} else {
SearchResult temp;
var score = Evaluation (board, cell, player);
achievable.Count += 1;
foreach (var _cell in emptyCells)
{
_cell.Player = player;
temp = -ABNegamax (board, _cell, height-1, -hope, -achievable, -player);
temp.Score += score;
_cell.Player = 0;
if (temp.Score >= hope.Score) {
return temp;
}
achievable.Count = temp.Count = achievable.Count + temp.Count;
achievable = temp.Score >= achievable.Score ? temp : achievable;
}
return achievable;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="Yavalath.Board"/> class.
/// </summary>
public Board()
{
var count = 0;
for(var i = 0; i < Cells.Length; i++) {
var playable = PlayableCells[i] == 1;
if(i % DIMENSION == 0) count = 1;
if(playable) count++;
Cells[i] = new Cell(Borders[i],
playable: playable,
index: i,
position: playable ?
String.Format("{0}{1}", (char)('A'-1+(i/DIMENSION)), count-1) : ""
);
}
}
/// <summary>
/// Evaluate the score for a specific <see cref="Yavalath.Cell"/>.
/// </summary>
/// <param name='gameBoard'>
/// Game board.
/// </param>
/// <param name='cell'>
/// Cell.
/// </param>
/// <param name='playerSymbol'>
/// Player symbol.
/// </param>
/// <param name='patterns'>
/// Patterns.
/// </param>
public static double Evaluation(Board gameBoard, Cell cell, int playerSymbol, Pattern[] patterns = null)
{
if(patterns == null) patterns = Patterns(playerSymbol);
var patterns2 = Patterns (-playerSymbol);
var t = cell.Player;
cell.Player = 0;
var lines = GetLines(gameBoard, cell);
var preScore = GetScore(lines, patterns) + GetScore(lines, patterns2);
cell.Player = t;
lines = GetLines(gameBoard, cell);
var postScore = GetScore(lines, patterns) + 2*GetScore(lines, patterns2);
return postScore - preScore;
}
/// <summary>
/// Gets the correcponding row and diagonals for a <see cref="Yavalath.Cell"/>.
/// </summary>
/// <returns>
/// The player values for each cell.
/// </returns>
/// <param name='gameBoard'>
/// The Game board.
/// </param>
/// <param name='cell'>
/// The Cell.
/// </param>
private static int[][] GetLines(Board gameBoard, Cell cell)
{
Func<Cell, int> getPlayer = c => c.Player;
var t = gameBoard.UpDiagonal (cell).Select (getPlayer).ToArray ();
return new int[][]{
gameBoard.UpDiagonal (cell).Select (getPlayer).ToArray (),
gameBoard.DownDiagonal (cell).Select (getPlayer).ToArray (),
gameBoard.Row (cell).Select (getPlayer).ToArray () };
}
public List<Cell> UpDiagonal(Cell cell)
{
return UpDiagonal(cell.Index);
}
public List<Cell> Row(Cell cell)
{
return Row(cell.Index);
}
