/// <summary>
/// Determines value equality.
/// </summary>
/// <param name="other">The other object to compare against.</param>
/// <returns>True if the objects are equal.</returns>
/// TODO: Should this be virtual?
protected virtual bool IsEqual(DefaultMutablePath <V, E> other)
{
return(Src.Equals(other.Src) &&
Dst.Equals(other.Dst) &&
Cost.Equals(other.Cost) &&
Edges.SequenceEqual(other.Edges));
}
/// <inheritdoc/>
public bool Equals(DefaultMutablePath <V, E> other)
{
if (other is null)
{
return(false);
}
if (ReferenceEquals(this, other))
{
return(true);
}
return(IsEqual(other));
}
/// <summary>
/// Builds a set of all paths between the source and destination using the graph search
/// result by applying breadth-first search through the parent edges and vertex costs.
/// </summary>
/// <param name="result">The graph search result.</param>
/// <param name="src">The source vertex.</param>
/// <param name="dst">The destination vertex.</param>
/// <param name="maxPaths">The limit on the number of paths built, <see cref="AllPaths"/> for no limit.</param>
private static void BuildAllPaths(DefaultResult result, V src, V dst, int maxPaths = AllPaths)
{
var basePath = new DefaultMutablePath <V, E>();
basePath.Cost = result.GetCost(dst);
var pendingPaths = new HashSet <DefaultMutablePath <V, E> >();
pendingPaths.Add(basePath);
while (pendingPaths.Count != 0 &&
(maxPaths == AllPaths || result.Paths.Count < maxPaths))
{
var frontier = new HashSet <DefaultMutablePath <V, E> >();
foreach (DefaultMutablePath <V, E> path in pendingPaths)
{
// For each pending path, locate its first vertex
// since we will be moving backwards from it.
V firstVertex = GetFirstVertex(path, dst);
// If the first vertex is our expected source, we have reached
// the beginning, so add this path to the result paths.
if (firstVertex.Equals(src))
{
path.Cost = result.GetCost(dst);
result.Paths.Add(new DefaultPath <V, E>(path.Edges, path.Cost));
}
else
{
// If we have not reached the beginning, i.e. the source, fetch the
// set of edges leading to the first vertex of this pending path.
// If there are none, abandon processing this path for good.
ISet <E> firstVertexParents = result.Parents.GetOrDefault(firstVertex, new HashSet <E>());
if (firstVertexParents is null || firstVertexParents?.Count is 0)
{
break;
}
// Now, iterate over all the edges and for each of them cloning the current
// path and then inserting that edge to the path and adding that path to the
// pending ones. When processing the last edge, modify the current pending
// path rather than cloning a new one.
List <E> edges = firstVertexParents.ToList();
for (int i = 0; i < edges.Count; ++i)
{
E edge = edges[i];
bool isLast = i == edges.Count - 1;
// Exclude any looping paths.
if (!IsInPath(edge, path))
{
DefaultMutablePath <V, E> pendingPath = isLast ? path : new DefaultMutablePath <V, E>(path);
pendingPath.InsertEdge(edge);
frontier.Add(pendingPath);
}
}
}
}
// All pending paths have been scaned, so promote the next frontier.
pendingPaths = frontier;
}
}
