/**
* 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();
}
/**
* 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();
}
}
private int[] rank; // rank[v] = rank of vertex v in order
/**
* Determines whether the digraph {@code G} has a topological order and, if so,
* finds such a topological order.
* @param G the digraph
*/
public Topological(Digraph G) {
DirectedCycle finder = new DirectedCycle(G);
if (!finder.hasCycle()) {
DepthFirstOrder dfs = new DepthFirstOrder(G);
order = dfs.reversePost();
rank = new int[G.V()];
int i = 0;
for (int v : order)
rank[v] = i++;
}
}
private int count; // number of strongly-connected components
/**
* Computes the strong components of the digraph {@code G}.
* @param G the digraph
*/
public KosarajuSharirSCC(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);
}