/// <summary>
/// Returns last step of the solution, or default value of <typeparamref name="TFactor"/> if solution is not found.
/// </summary>
/// <typeparam name="TFactor">The type of factor used to evaluate with heuristic function. The type is projected from <typeparamref name="TStep"/>.</typeparam>
/// <typeparam name="TStep">The type of step of the problem.</typeparam>
/// <param name="source">The current instance.</param>
/// <returns>The last step of the solution.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is null.</exception>
/// <exception cref="InvalidOperationException">
/// The orderby clause is missing or <typeparamref name="TFactor"/> does not implement <see cref="IComparable{TFactor}"/> interface.
/// </exception>
public static TFactor LastOrDefault <TFactor, TStep>(this HeuristicSearchBase <TFactor, TStep> source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
var lastNode = source.Run();
if (lastNode == null)
{
return(default(TFactor));
}
return(source.IsReversed ? lastNode.TraceBack().Factor : lastNode.Factor);
}
/// <summary>
/// Returns last step of the solution.
/// </summary>
/// <typeparam name="TFactor">The type of factor used to evaluate with heuristic function. The type is projected from <typeparamref name="TStep"/>.</typeparam>
/// <typeparam name="TStep">The type of step of the problem.</typeparam>
/// <param name="source">The current instance.</param>
/// <returns>The last step of the solution.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is null.</exception>
/// <exception cref="InvalidOperationException">Solution is not found.</exception>
public static TFactor Last <TFactor, TStep>(this HeuristicSearchBase <TFactor, TStep> source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
var lastNode = source.Run();
if (lastNode == null)
{
throw new InvalidOperationException("Sequence contains no elements.");
}
return(source.IsReversed ? lastNode.TraceBack().Factor : lastNode.Factor);
}