/// <summary>
/// Connects two vertices together with a weight, in the direction: first->second.
/// </summary>
public bool AddEdge(T source, T destination, int weight)
{
// Check existence of nodes, the validity of the weight value, and the non-existence of edge
if (weight == EMPTY_EDGE_VALUE)
{
return(false);
}
else if (!HasVertex(source) || !HasVertex(destination))
{
return(false);
}
else if (_doesEdgeExist(source, destination))
{
return(false);
}
// Add edge from source to destination
var edge = new WeightedEdge <T>(source, destination, weight);
_adjacencyList[source].Append(edge);
// Increment edges count
++_edgesCount;
return(true);
}
/// <summary>
/// Get all outgoing weighted edges from vertex
/// </summary>
public virtual IEnumerable <WeightedEdge <T> > OutgoingEdges(T vertex)
{
if (!HasVertex(vertex))
{
return(null);
}
int source = _vertices.IndexOf(vertex);
var list = new DLinkedList <WeightedEdge <T> >();
// Check existence of vertex
if (source != -1)
{
for (int adjacent = 0; adjacent < _vertices.Count; ++adjacent)
{
if (_vertices[adjacent] != null && _doesEdgeExist(source, adjacent))
{
var edge = new WeightedEdge <T>(
(T)_vertices[source],
(T)_vertices[adjacent],
_getEdgeWeight(source, adjacent));
list.Append(edge);
}
}
}
return(list);
}
public int CompareTo(WeightedEdge <T> other)
{
bool areNodesEqual = Source.IsEqualTo <T>(other.Source) && Destination.IsEqualTo <T>(other.Destination);
if (!areNodesEqual)
{
return(-1);
}
else
{
return(Weight.CompareTo(other.Weight));
}
}
/// <summary>
/// Helper function. Returns edge object from source to destination, if exists; otherwise, null.
/// </summary>
protected virtual WeightedEdge <T> _tryGetEdge(T source, T destination)
{
WeightedEdge <T> edge = null;
try
{
edge = _adjacencyList[source].FindFirst(item => item.Source.IsEqualTo <T>(source) && item.Destination.IsEqualTo <T>(destination));
}
catch (Exception)
{
return(null);
}
// Could return a null object.
return(edge);
}
/// <summary>
/// Helper function. Returns edge object from source to destination, if exists; otherwise, null.
/// </summary>
protected virtual WeightedEdge <T> _tryGetEdge(T source, T destination)
{
WeightedEdge <T> edge = null;
// Predicate
var sourceToDestinationPredicate = new Predicate <WeightedEdge <T> >((item) => item.Source.IsEqualTo <T>(source) && item.Destination.IsEqualTo <T>(destination));
// Try to find a match
if (_adjacencyList.ContainsKey(source))
{
_adjacencyList[source].TryFindFirst(sourceToDestinationPredicate, out edge);
}
// Return!
// Might return a null object.
return(edge);
}
/// <summary>
/// Get all incoming directed weighted edges to a vertex.
/// </summary>
public virtual IEnumerable <WeightedEdge <T> > IncomingEdges(T vertex)
{
if (!HasVertex(vertex))
{
throw new KeyNotFoundException("Vertex doesn't belong to graph.");
}
var predicate = new Predicate <WeightedEdge <T> >((edge) => edge.Destination.IsEqualTo(vertex));
foreach (var adjacent in _adjacencyList.Keys)
{
WeightedEdge <T> incomingEdge = null;
if (_adjacencyList[adjacent].TryFindFirst(predicate, out incomingEdge))
{
yield return(incomingEdge);
}
}//end-foreach
}
/// <summary>
/// Helper function. Returns edge object from source to destination, if exists; otherwise, null.
/// </summary>
protected virtual WeightedEdge <T> _tryGetEdge(T source, T destination)
{
var success = false;
WeightedEdge <T> edge = null;
var sourceToDestinationPredicate = new Predicate <WeightedEdge <T> >((item) => item.Source.IsEqualTo <T>(source) && item.Destination.IsEqualTo <T>(destination));
var destinationToSourcePredicate = new Predicate <WeightedEdge <T> >((item) => item.Source.IsEqualTo <T>(destination) && item.Destination.IsEqualTo <T>(source));
if (_adjacencyList.ContainsKey(source))
{
success = _adjacencyList[source].TryFindFirst(sourceToDestinationPredicate, out edge);
}
if (!success && _adjacencyList.ContainsKey(destination))
{
_adjacencyList[destination].TryFindFirst(destinationToSourcePredicate, out edge);
}
// Could return a null object.
return(edge);
}