/// <summary>
/// Evaluate the current node, looking for the best match that keep the game playing.
/// </summary>
/// <param name="node"></param>
/// <param name="depth"></param>
/// <param name="maximizingPlayer"></param>
/// <param name="forceSearch"></param>
/// <returns>The value that thinks it's better to continue the game.</returns>
public IValueContainer <T, V> Evaluate(Node <T> node, int depth, bool maximizingPlayer, bool forceSearch)
{
IValueContainer <T, V> result = new ValueContainer <T, V>();
ICollection <IValueContainer <T, V> > results = new List <IValueContainer <T, V> >();
// Sometimes it's needed to force the search. For example if the value is less than some condition.
if (!forceSearch && (depth == 0 || node.Terminal))
{
return(heuristic.Evaluate(node.Value));
}
// Maximize the gain between own best play and opponents best play.
if (maximizingPlayer)
{
results.Add(minusInfinity);
foreach (Node <T> child in node.Children)
{
// Get the best child for this player
IValueContainer <T, V> maxOfChild = Max(minusInfinity, Evaluate(child, depth - 1, false, false));
// If the result of this node is better that what we have before, this is our new record.
if (maxOfChild.CompareTo(results.First()) > 0)
{
results.Clear();
results.Add(maxOfChild);
}
// If the result if the same, add it to the list
else if (maxOfChild.CompareTo(results.First()) == 0)
{
results.Add(maxOfChild);
}
// Ignore if not better or equal
}
}
else
{
results.Add(plusInfinity);
foreach (Node <T> child in node.Children)
{
// Get the best child for this player
IValueContainer <T, V> minOfChild = Min(plusInfinity, Evaluate(child, depth - 1, true, false));
// If the result of this node is better that what we have before, this is our new record.
if (minOfChild.CompareTo(results.First()) < 0)
{
results.Clear();
results.Add(minOfChild);
}
// If the result if the same, add it to the list
else if (minOfChild.CompareTo(results.First()) == 0)
{
results.Add(minOfChild);
}
// Ignore if not better or equal
}
}
return(results.ElementAt(random.Next(0, results.Count())));
}
private IValueContainer <T, V> Min(IValueContainer <T, V> first, IValueContainer <T, V> second)
{
return(first.CompareTo(second) < 0 ? first : second);
}
