/**
* Determines whether the edge-weighted digraph <tt>G</tt> 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();
}
}
public KosarajuSCC(Digraph G) {
marked = new boolean[G.V()];
id = new int[G.V()];
DepthFirstOrder order = new DepthFirstOrder(G.reverse());
for (int s : order.reverse())
if (!marked[s]) {
dfs(G, s);
count++;
}
}
private KosarajuSharirSCC(Digraph<V> digraph) {
ids = new HashMap<>(digraph.vertexCount());
visited = new HashSet<>(digraph.vertexCount());
size = new int[digraph.vertexCount()];
DepthFirstOrder<V> dfo = DepthFirstOrder.from(digraph.reverse());
for (V vertex : dfo.reversePost()) {
if (!visited.contains(vertex)) {
dfs(digraph, vertex);
count++;
}
}
}
public KosarajuSCC(Digraph G) {
// compute reverse postorder of reverse graph
DepthFirstOrder dfs = new DepthFirstOrder(G.reverse());
// run DFS on G, using reverse postorder to guide calculation
marked = new boolean[G.V()];
id = new int[G.V()];
for (int v : dfs.reversePost()) {
if (!marked[v]) {
dfs(G, v);
count++;
}
}
// check that id[] gives strong components
assert check(G);
}
/**
* Unit tests the {@code DepthFirstOrder} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
In in = new In(args[0]);
Digraph G = new Digraph(in);
DepthFirstOrder dfs = new DepthFirstOrder(G);
StdOut.println(" v pre post");
StdOut.println("--------------");
for (int v = 0; v < G.V(); v++) {
StdOut.printf("%4d %4d %4d\n", v, dfs.pre(v), dfs.post(v));
}
StdOut.print("Preorder: ");
for (int v : dfs.pre()) {
StdOut.print(v + " ");
}
StdOut.println();
StdOut.print("Postorder: ");
for (int v : dfs.post()) {
StdOut.print(v + " ");
}
StdOut.println();
StdOut.print("Reverse postorder: ");
for (int v : dfs.reversePost()) {
StdOut.print(v + " ");
}
StdOut.println();
}
