public static int ComputeShortestPath(IDirectedGraph <int> graph, int startVertex, int endVertex)
{
if (startVertex == endVertex)
{
return(0);
}
// Key - Node, Value - node distance from startVertex
var exploredVertices = new Dictionary <int, int> {
{ startVertex, 0 }
};
var queue = new Queue <int>();
queue.Enqueue(startVertex);
while (queue.Any())
{
int v = queue.Dequeue();
foreach (int w in graph.GetAdjacentVertices(v))
{
if (!exploredVertices.ContainsKey(w))
{
int dist = exploredVertices[v] + 1;
exploredVertices.Add(w, dist);
queue.Enqueue(w);
}
}
}
return(exploredVertices.ContainsKey(endVertex) ? exploredVertices[endVertex] : int.MinValue);
}
private static void DfsFindSccs(IDirectedGraph <int> graph,
int startVertex,
HashSet <int> exploredVertices,
List <int> sccs)
{
var stack = new Stack <int>();
stack.Push(startVertex);
while (stack.Any())
{
int v = stack.Peek();
if (!exploredVertices.Contains(v))
{
exploredVertices.Add(v);
}
bool hasUnexploredNeighbours = false;
foreach (int w in graph.GetAdjacentVertices(v))
{
if (!exploredVertices.Contains(w))
{
hasUnexploredNeighbours = true;
stack.Push(w);
break;
}
}
if (!hasUnexploredNeighbours)
{
sccs.Add(stack.Pop());
}
}
}
public static IDirectedGraph <int> ReverseGraph(IDirectedGraph <int> graph)
{
var reversedGraph = new DirectedGraphAdjList <int>(saveReversedVersion: false,
vertices: graph.GetVertices().ToArray());
foreach (int v in graph.GetVertices())
{
foreach (int w in graph.GetAdjacentVertices(v))
{
reversedGraph.AddEdge(w, v);
}
}
return(reversedGraph);
}
public static IEnumerable <int> BreadthFirst(IDirectedGraph <int> graph, int startVertex)
{
var exploredVertices = new HashSet <int> {
startVertex
};
var queue = new Queue <int>();
queue.Enqueue(startVertex);
while (queue.Any())
{
int v = queue.Dequeue();
yield return(v);
foreach (int w in graph.GetAdjacentVertices(v))
{
if (!exploredVertices.Contains(w))
{
exploredVertices.Add(w);
queue.Enqueue(w);
}
}
}
}
public static IEnumerable <int> DepthFirst(IDirectedGraph <int> graph, int startVertex)
{
var exploredVertices = new HashSet <int> {
startVertex
};
var stack = new Stack <int>();
stack.Push(startVertex);
while (stack.Any())
{
int v = stack.Pop();
yield return(v);
foreach (int w in graph.GetAdjacentVertices(v))
{
if (!exploredVertices.Contains(w))
{
exploredVertices.Add(w);
stack.Push(w);
}
}
}
}
