/**
* Determines whether the edge-weighted digraph {@code G} has a topological
* order and, if so, finds such an order.
* @param G the edge-weighted digraph
*/
public Topological(EdgeWeightedDigraph G) {
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(G);
if (!finder.hasCycle()) {
DepthFirstOrder dfs = new DepthFirstOrder(G);
order = dfs.reversePost();
}
}
/**
* Unit tests the {@code EdgeWeightedDirectedCycle} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
// create random DAG with V vertices and E edges; then add F random edges
int V = Integer.parseInt(args[0]);
int E = Integer.parseInt(args[1]);
int F = Integer.parseInt(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));
}
StdOut.println(G);
// find a directed cycle
EdgeWeightedDirectedCycle finder = new EdgeWeightedDirectedCycle(G);
if (finder.hasCycle()) {
StdOut.print("Cycle: ");
for (DirectedEdge e : finder.cycle()) {
StdOut.print(e + " ");
}
StdOut.println();
}
// or give topologial sort
else {
StdOut.println("No directed cycle");
}
}