private bool GetUnvistedEdge(AbstractDiGraph <TNode> graph, TNode sourceNode, out TNode destinationNode)
{
destinationNode = default(TNode);
bool hasUnvistitedNodes = graph.GetNeighbourNodes(sourceNode)
.Any(
y =>
!_vistedEdges.Any(x => x.Item1.Equals(sourceNode) && x.Item2.Equals(y)));
if (hasUnvistitedNodes)
{
destinationNode = graph.GetNeighbourNodes(sourceNode)
.First(
y => !_vistedEdges.Any(x => x.Item1.Equals(sourceNode) && x.Item2.Equals(y)));
}
return(hasUnvistitedNodes);
}
public AbstractGraphPath <TNode> GetShortestPath(AbstractDiGraph <TNode> graph, TNode sourceNode,
TNode destinationNode)
{
//Validate Input
if (graph == null)
{
throw new ArgumentNullException("graph");
}
if (graph.AllEdges.Any(x => x.Item3 <= 0))
{
throw new InvalidEdgeWeightException(
string.Format("The graph contains one or more edges with edge weight less than or equal to zero"));
}
//Initialise data structures
Initialise(graph, sourceNode);
//Compute Shortest Path
while (_shortestPathUnKnownNodesQueue.Any() && !_shortestPathKnownNodes.Contains(destinationNode))
{
foreach (var shortestPathKnownNode in _shortestPathKnownNodes)
{
foreach (
var neighbour in
graph.GetNeighbourNodes(shortestPathKnownNode)
.Where(x => !_shortestPathKnownNodes.Contains(x)))
{
int edgeWeight = graph.GetEdgeWeight(shortestPathKnownNode, neighbour);
int newestimatedDistance = _estimatedDistances[shortestPathKnownNode].PathWeight +
edgeWeight;
if (IsEstimatedDistanceBetter(neighbour, newestimatedDistance))
{
_estimatedDistances[neighbour].PathWeight = newestimatedDistance;
_predessorNodes[neighbour] = shortestPathKnownNode;
}
}
}
DequeueShortestPathKnownNode();
}
CompletePaths();
var result = _estimatedDistances.SingleOrDefault(x => x.Value.DestinationNode.Equals(destinationNode)).Value;
if (result.PathWeight == Infinity)
{
return(null);
}
return(result);
}
private void DFSVisit(AbstractDiGraph <TNode> graph, TNode node)
{
_startTime[node] = ++_time;
foreach (TNode neighbour in graph.GetNeighbourNodes(node))
{
var dfsEdge = new DepthFirstSearchEdge <TNode> {
SourceNode = node, DestinationNode = neighbour
};
dfsEdge.EdgeWeight = graph.GetEdgeWeight(dfsEdge.SourceNode, dfsEdge.DestinationNode);
_dfsEdges.Add(dfsEdge);
bool isNeighbourVisited = IsNodeinParentOrChild(neighbour);
if (!isNeighbourVisited)
{
_parent[neighbour] = node;
dfsEdge.EdgeType = DepthFirstSearchEdgeType.TreeEdge;
DFSVisit(graph, neighbour);
}
else if (!_endTime.ContainsKey(neighbour))
{
dfsEdge.EdgeType = DepthFirstSearchEdgeType.BackEdge;
}
else if (_startTime[node] < _startTime[neighbour])
{
dfsEdge.EdgeType = DepthFirstSearchEdgeType.ForwardEdge;
}
else
{
dfsEdge.EdgeType = DepthFirstSearchEdgeType.CrossEdge;
}
}
_endTime[node] = ++_time;
_order.Add(node, _order.Count + 1);
}
