public static void MainTest(string[] args)
{
// create random DAG with V vertices and E edges; then add F random edges
int V = int.Parse(args[0]);
int E = int.Parse(args[1]);
int F = int.Parse(args[2]);
EdgeWeightedDigraph G = new EdgeWeightedDigraph(V);
int[] vertices = new int[V];
for (int i = 0; i < V; i++)
{
vertices[i] = i;
}
StdRandom.Shuffle(vertices);
for (int i = 0; i < E; i++)
{
int v, w;
do
{
v = StdRandom.Uniform(V);
w = StdRandom.Uniform(V);
} while (v >= w);
double weight = StdRandom.Uniform();
G.AddEdge(new DirectedEdge(v, w, weight));
}
// add F extra edges
for (int i = 0; i < F; i++)
{
int v = StdRandom.Uniform(V);
int w = StdRandom.Uniform(V);
double weight = StdRandom.Uniform(0.0, 1.0);
G.AddEdge(new DirectedEdge(v, w, weight));
}
Console.WriteLine(G);
// find a directed cycle
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(G);
if (finder.HasCycle)
{
Console.Write("Cycle: ");
foreach (DirectedEdge e in finder.GetCycle())
{
Console.Write(e + " ");
}
Console.WriteLine();
}
// or give topologial sort
else
{
Console.WriteLine("No directed cycle");
}
}
/// <summary>
/// Determines whether the edge-weighted digraph <c>G</c> has a topological
/// order and, if so, finds such an order.</summary>
/// <param name="G">the edge-weighted digraph</param>
///
public Topological(EdgeWeightedDigraph G)
{
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(G);
if (!finder.HasCycle)
{
DepthFirstOrder dfs = new DepthFirstOrder(G);
order = dfs.ReversePost();
}
}
// by finding a cycle in predecessor graph
private void findNegativeCycle()
{
int V = edgeTo.Length;
EdgeWeightedDigraph spt = new EdgeWeightedDigraph(V);
for (int v = 0; v < V; v++)
{
if (edgeTo[v] != null)
{
spt.AddEdge(edgeTo[v]);
}
}
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(spt);
cycle = finder.GetCycle();
}
/// <summary>
/// Returns a negative cycle, or <c>null</c> if there is no such cycle.</summary>
/// <returns>a negative cycle as an iterable of edges,
/// or <c>null</c> if there is no such cycle</returns>
///
public IEnumerable <DirectedEdge> NegativeCycle()
{
for (int v = 0; v < distTo.Length; v++)
{
// negative cycle in v's predecessor graph
if (distTo[v, v] < 0.0)
{
int V = edgeTo.Length;
EdgeWeightedDigraph spt = new EdgeWeightedDigraph(V);
for (int w = 0; w < V; w++)
{
if (edgeTo[v, w] != null)
{
spt.AddEdge(edgeTo[v, w]);
}
}
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(spt);
Debug.Assert(finder.HasCycle);
return(finder.GetCycle());
}
}
return(null);
}
