// Single step of recursive DFS.
private static void dfsRecursiveStep <TVertexId, TVertexProperty, TEdgeProperty>(
this IGraph <TVertexId, TVertexProperty, TEdgeProperty> graph, IDfsStrategy <TVertexId> strategy,
DfsRecursiveState <TVertexId> state)
{
Vertex <TVertexId> vertex = state.vertex;
state.onEntry(vertex);
strategy.OnEntry(vertex);
foreach (Vertex <TVertexId> neighbour in graph.GetNeighbours(vertex))
{
if (!state.reached.ContainsKey(neighbour))
{
strategy.OnNextVertex(vertex, neighbour);
state.vertex = neighbour;
graph.dfsRecursiveStep(strategy, state);
}
else if (state.reached[neighbour] == state.iteration)
{
strategy.OnEdgeToVisited(vertex, neighbour);
}
}
strategy.OnExit(vertex);
state.onExit(vertex);
}
/// <summary>Iterative deph-first-search algorithm.</summary>
/// <param name="graph">a graph</param>
/// <param name="strategy">a searching strategy</param>
/// <param name="roots">starting vertices</param>
/// <returns>enumerable of visited vertices</returns>
public static IEnumerable <Vertex <TVertexId> > DfsIterative <TVertexId, TVertexProperty, TEdgeProperty>(
this IGraph <TVertexId, TVertexProperty, TEdgeProperty> graph, IDfsStrategy <TVertexId> strategy,
IEnumerable <Vertex <TVertexId> > roots)
{
var reached = new Dictionary <Vertex <TVertexId>, int>();
var vertexStack = new Stack <Vertex <TVertexId> >();
int iteration = 1;
foreach (Vertex <TVertexId> root in roots)
{
if (!reached.ContainsKey(root))
{
strategy.ForRoot(root);
vertexStack.Push(root);
while (vertexStack.Count != 0)
{
Vertex <TVertexId> vertex = vertexStack.Pop();
if (!reached.ContainsKey(vertex))
{
reached[vertex] = iteration;
strategy.OnEntry(vertex);
foreach (Vertex <TVertexId> neighbour in graph.GetNeighbours(vertex))
{
if (!reached.ContainsKey(neighbour))
{
strategy.OnNextVertex(vertex, neighbour);
vertexStack.Push(neighbour);
}
else if (reached[neighbour] == iteration)
{
strategy.OnEdgeToVisited(vertex, neighbour);
}
}
strategy.OnExit(vertex);
reached[root] = -iteration;
}
}
++iteration;
}
}
return(reached.Keys);
}
/// <summary>Recursive deph-first-search algorithm.</summary>
/// <param name="graph">a graph</param>
/// <param name="strategy">a searching strategy</param>
/// <param name="roots">starting vertices</param>
/// <returns>enumerable of visited vertices</returns>
public static IEnumerable <Vertex <TVertexId> > DfsRecursive <TVertexId, TVertexProperty, TEdgeProperty>(
this IGraph <TVertexId, TVertexProperty, TEdgeProperty> graph, IDfsStrategy <TVertexId> strategy,
IEnumerable <Vertex <TVertexId> > roots)
{
var state = new DfsRecursiveState <TVertexId>();
foreach (Vertex <TVertexId> root in roots)
{
if (!state.reached.ContainsKey(root))
{
strategy.ForRoot(root);
state.vertex = root;
graph.dfsRecursiveStep(strategy, state);
++state.iteration;
}
}
return(state.reached.Keys);
}