/// <summary>
/// Returns an inverted graph
/// </summary>
/// <returns></returns>
private ConnectivityCheck GetInvertedGraph()
{
ConnectivityCheck g = new ConnectivityCheck(numberOfVertices);
for (int v = 0; v < numberOfVertices; v++)
{
foreach (int i in adjacencyList[v])
{
g.adjacencyList[i].Add(v);
}
}
return(g);
}
/// <summary>
/// Checks if graph is valid
/// </summary>
public static bool IsGraphValid(Digraph digraph)
{
if (digraph.Vertices.Count < 3)
{
return(false);
}
ConnectivityCheck check = new ConnectivityCheck(digraph.Vertices.Count);
foreach (Arc arc in digraph.Arcs)
{
check.AddArc(arc);
}
return(check.IsStronglyConnected());
}
/// <summary>
/// Connectivity check method (using Kosaraju algorithm)
/// </summary>
public bool IsStronglyConnected()
{
bool[] visited = new bool[numberOfVertices];
// Fist DFS traversing
DFS(0, visited);
// Returning false there is a vertex that hasn't been visited
if (visited.Contains(false))
{
return(false);
}
// Inverting the graph
ConnectivityCheck gr = GetInvertedGraph();
visited = new bool[numberOfVertices]; // Refreshing
// DFS traversing for inverted graph
gr.DFS(0, visited);
// Returning false if there is a vertex that hasn't been visited
return(Array.TrueForAll(visited, v => v));
}