/**
* Concatenates the specified GraphWalk to the end of this GraphWalk. This action can only be
* performed if the end vertex of this GraphWalk is the same as the start vertex of the
* extending GraphWalk
*
* @param extension GraphPath used for the concatenation.
* @param walkWeightCalculator Function used to calculate the weight of the GraphWalk obtained
* after the concatenation.
* @return a GraphWalk that represents the concatenation of this object's walk followed by the
* walk specified in the extension argument.
*/
public GraphWalk <V, E> concat(
GraphWalk <V, E> extension, Func <GraphWalk <V, E>, Double> walkWeightCalculator)
{
if (this.isEmpty())
{
throw new ArgumentException("An empty path cannot be extended");
}
if (!this.endVertex.Equals(extension.getStartVertex()))
{
throw new ArgumentException(
"This path can only be extended by another path if the end vertex of the orginal path and the start vertex of the extension are equal.");
}
List <V> concatVertexList = null;
List <E> concatEdgeList = null;
if (vertexList != null)
{
concatVertexList = new List <V>(this.vertexList);
List <V> vertexListExtension = extension.getVertexList();
concatVertexList.AddRange(vertexListExtension.Skip(1));
}
if (edgeList != null)
{
concatEdgeList = new List <E>(this.edgeList);
concatEdgeList.AddRange(extension.getEdgeList());
}
GraphWalk <V, E> gw = new GraphWalk <V, E>(
this.graph, startVertex, extension.getEndVertex(), concatVertexList, concatEdgeList, 0);
gw.setWeight(walkWeightCalculator(gw));
return(gw);
}
public bool Equals(GraphWalk <V, E> o)
{
if (o == null || !(o is GraphWalk <V, E>))
{
return(false);
}
else if (this == o)
{
return(true);
}
GraphWalk <V, E> other = (GraphWalk <V, E>)o;
if (this.isEmpty() && other.isEmpty())
{
return(true);
}
if (!this.startVertex.Equals(other.getStartVertex()) ||
!this.endVertex.Equals(other.getEndVertex()))
{
return(false);
}
// If this path is expressed as a vertex list, we may get away by comparing the other path's
// vertex list
// This only works if its vertexList identifies a unique path in the graph
if (this.edgeList == null && !other.getGraph().getType().isAllowingMultipleEdges())
{
return(this.vertexList.Equals(other.getVertexList()));
}
else // Unlucky, we need to compare the edge lists,
{
return(this.getEdgeList().Equals(other.getEdgeList()));
}
}
/**
* {@inheritDoc}
*/
public GraphPath <V, E> getPath(V targetVertex)
{
if (source.Equals(targetVertex))
{
return(GraphWalk <V, E> .singletonWalk(g, source, 0d));
}
List <E> edgeList = new List <E>();
V cur = targetVertex;
KeyValuePair <Double, E> p;
bool find = map.TryGetValue(cur, out p);
if (!find || p.Key.Equals(Double.PositiveInfinity))
{
return(null);
}
double weight = 0d;
while (find && !p.Equals(source))
{
E e = p.Value;
if (e == null)
{
break;
}
edgeList.Insert(0, e);
weight += g.getEdgeWeight(e);
cur = Graphs.getOppositeVertex(g, e, cur);
find = map.TryGetValue(cur, out p);
}
return(new GraphWalk <V, E>(g, source, targetVertex, null, edgeList, weight));
}
/**
* Create an empty path. Returns null if the source vertex is different than the target vertex.
*
* @param source the source vertex
* @param sink the sink vertex
* @return an empty path or null null if the source vertex is different than the target vertex
*/
protected GraphPath <V, E> createEmptyPath(V source, V sink)
{
if (source.Equals(sink))
{
return(GraphWalk <V, E> .singletonWalk(graph, source, 0d));
}
else
{
return(null);
}
}
/**
* {@inheritDoc}
*/
public GraphPath <V, E> getPath(V targetVertex)
{
GraphPath <V, E> p = paths[targetVertex];
if (p == null)
{
if (source.Equals(targetVertex))
{
return(GraphWalk <V, E> .singletonWalk(graph, source, 0d));
}
else
{
return(null);
}
}
else
{
return(p);
}
}
/**
* Reverses the direction of the walk. In case of directed/mixed graphs, the arc directions will
* be reversed. An exception is thrown if reversing an arc (u,v) is impossible because arc (v,u)
* is not present in the graph.
*
* @param walkWeightCalculator Function used to calculate the weight of the reversed GraphWalk
* @throws InvalidGraphWalkException if the path is invalid
* @return a reversed GraphWalk
*/
public GraphWalk <V, E> reverse(Func <GraphWalk <V, E>, Double> walkWeightCalculator)
{
List <V> revVertexList = null;
List <E> revEdgeList = null;
double revWeight = 0;
if (vertexList != null)
{
revVertexList = new List <V>(this.vertexList);
revVertexList.Reverse();
if (graph.getType().isUndirected())
{
revWeight = this.weight;
}
// Check validity of the path. If the path is invalid, then calculating its weight may
// result in an undefined exception.
// If an edgeList is provided, then this check can be postponed to the construction of
// the reversed edge list
if (!graph.getType().isUndirected() && edgeList == null)
{
for (int i = 0; i < revVertexList.Count - 1; i++)
{
V u = revVertexList[i];
V v = revVertexList[i + 1];
E edge = graph.getEdge(u, v);
if (edge == null)
{
throw new ArgumentException(
"this walk cannot be reversed. The graph does not contain a reverse arc for arc "
+ graph.getEdge(v, u));
}
else
{
revWeight += graph.getEdgeWeight(edge);
}
}
}
}
if (edgeList != null)
{
revEdgeList = new List <E>(this.edgeList.Count);
if (graph.getType().isUndirected())
{
revEdgeList.AddRange(this.edgeList);
revEdgeList.Reverse();
revWeight = this.weight;
}
else
{
var listIterator = edgeList.GetEnumerator();
while (listIterator.MoveNext())
{
E e = listIterator.Current;
V u = graph.getEdgeSource(e);
V v = graph.getEdgeTarget(e);
E revEdge = graph.getEdge(v, u);
if (revEdge == null)
{
throw new ArgumentException(
"this walk cannot be reversed. The graph does not contain a reverse arc for arc "
+ e);
}
revEdgeList.Add(revEdge);
revWeight += graph.getEdgeWeight(revEdge);
}
}
}
// Update weight of reversed walk
GraphWalk <V, E> gw = new GraphWalk <V, E>(
this.graph, this.endVertex, this.startVertex, revVertexList, revEdgeList, 0);
if (walkWeightCalculator == null)
{
gw.weight = revWeight;
}
else
{
gw.weight = walkWeightCalculator(gw);
}
return(gw);
}
