/// <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.Game"/> class.
/// </summary>
/// <param name='player1'>
/// Player1.
/// </param>
/// <param name='player2'>
/// Player2.
/// </param>
public Game(Player player1, Player player2)
{
GameBoard = new Board();
Players = new Dictionary<Player, int>(){
{player1, -1},
{player2, 1}
};
CurrentPlayer = player1;
}
// public static SearchResult Negamax (Board board, Cell cell, int player, int height,
// int oldscore = 0, Pattern[] patterns = null)
public override string GetNextMove(Board board, int playerSymbol)
{
Score -= board.Latest.Score;
var s = Algorithms.ABNegamax(board, board.Latest.Cell, SearchDepth,
new Algorithms.SearchResult {Score = -1.0/0, Count = 0},
new Algorithms.SearchResult {Score = 1.0/0}, playerSymbol);
Score = s.Score;
Console.WriteLine("Position: {0}; Evaluation count: {1}", s.Cell.Position, s.Count);
return s.Cell.Position;
}
/// <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 abstract string GetNextMove(Board board = null, int playerSymbol = 0);
public override string GetNextMove(Board board, int playerSymbol)
{
Console.Write("Take your move: [CellCoords] or \"TakeOver\"");
var input = Console.ReadLine();
return input;
}
