public static (IMove move, int score) AlphaBeta(IGame game, char player, char original, int ply, int alpha, int beta)
{
if (ply == 0 || game.IsWon() || !game.GetValidMoves(player).Any())
{
return(null, game.Evaluate(original));
}
(IMove move, int score)best = (null, 0);
var moves = game.GetValidMoves(player);
foreach (var move in moves)
{
if (move.IsValid(game))
{
move.Execute(game);
var(_, score) = AlphaBeta(game, game.NextPlayer(player), original, ply - 1, alpha, beta);
move.Undo(game);
if (best.move == null)
{
best = (move, score);
}
if (player == original)
{
if (score > best.score)
{
best = (move, score);
}
if (alpha < best.score)
{
alpha = best.score;
}
if (alpha >= beta)
{
break;
}
}
else
{
if (score < best.score)
{
best = (move, score);
}
if (beta > best.score)
{
beta = best.score;
}
if (beta <= alpha)
{
break;
}
}
}
}
return(best);
}
