private static double recursion(IExplorable node, int depth, double alpha, double beta, bool maximizing, int playCount)
{
if (depth == 0 || node.IsTerminal())
{
return(node.HeuresticValue(playCount));
}
if (maximizing)
{
double v = -inf;
foreach (var child in node.Explore())
{
v = Math.Max(v, AlphaBeta.recursion(child, depth - 1, alpha, beta, false, playCount + 1));
alpha = Math.Max(alpha, v);
if (beta <= alpha)
{
break;
}
}
return(v);
}
else
{
double v = inf;
foreach (var child in node.Explore())
{
v = Math.Min(v, AlphaBeta.recursion(child, depth - 1, alpha, beta, true, playCount + 1));
beta = Math.Min(beta, v);
if (beta <= alpha)
{
break;
}
}
return(v);
}
}
public static IExplorable BestMove(IExplorable node, int depth, bool maximizing)
{
IExplorable best_child = null;
double alpha = -inf, beta = inf;
if (maximizing)
{
double v = -inf;
foreach (var child in node.Explore())
{
var v2 = AlphaBeta.recursion(child, depth - 1, alpha, beta, false, 1);
if (v2 > v)
{
v = v2;
best_child = child;
}
alpha = Math.Max(alpha, v);
if (beta <= alpha)
{
break;
}
}
return(best_child);
}
else
{
double v = inf;
foreach (var child in node.Explore())
{
var v2 = AlphaBeta.recursion(child, depth - 1, alpha, beta, true, 1);
if (v2 < v)
{
v = v2;
best_child = child;
}
beta = Math.Min(beta, v);
if (beta <= alpha)
{
break;
}
}
return(best_child);
}
}