C++ Digraph::n方法代码示例

void toposort(Digraph& dg, int *pos, int *vert) {
// Compute a topological ordering of dg. On return, pos[u]
// is the position of vertex u in the ordering and vert[i]
// is the vertex in the i-th position in the ordering.
	int i; vertex u,v; edge e;
	UiList q(dg.n());
	int *nin = new int[dg.n()+1];

	// Let nin[u]=in-degree of u and put nodes u with nin[u]=0 on q
	for (u = 1; u <= dg.n(); u++) {
		nin[u] = 0;
		for (e = dg.firstIn(u); e != 0; e=dg.nextIn(u,e)) {
			nin[u]++;
		}
		if (nin[u] == 0) q.addLast(u);
	}
	i = 0;
	while (!q.empty()) { // q contains nodes u with nin[u] == 0
		u = q.first(); q.removeFirst(); pos[u] = ++i; vert[i] = u;
		for (e = dg.firstOut(u); e != 0; e = dg.nextOut(u,e)) {
			v = dg.head(e);
			if ((--(nin[v])) == 0) q.addLast(v);
		}
	}
	if (i < dg.n()) fatal("toposort: graph has cycle");
}

void KosarajuSCC::dfs(Digraph& dg, int v) {
	marked[v] = true;
	id[v] = count;

	for (int w = dg.first(v); w < dg.n(); w = dg.next(v, w)) {
		if (!marked[w])
			dfs(dg, w);
	}
}

/** Compute a topological ordering of dg.
 *  @param dg is a reference to an acyclic digraph
 *  @param vlist is a List object in which result is returned;
 *  on return, the vertices in vlist are in topogical order
 */
bool toposort(const Digraph& dg, List& vlist) {
	List q(dg.n());
	int *nin = new int[dg.n()+1];

	if (vlist.n() < dg.n()) vlist.resize(dg.n());
	else vlist.clear();

	// Let nin[u]=in-degree of u and put nodes u with nin[u]=0 on q
	for (vertex u = 1; u <= dg.n(); u++) {
		nin[u] = 0;
		for (edge e = dg.firstIn(u); e != 0; e = dg.nextIn(u,e)) {
			nin[u]++;
		}
		if (nin[u] == 0) q.addLast(u);
	}
	int i = 0;
	while (!q.empty()) { // q contains nodes u with nin[u] == 0
		vertex u = q.first(); q.removeFirst(); vlist.addLast(u); i++;
		for (edge e = dg.firstOut(u); e != 0; e = dg.nextOut(u,e)) {
			vertex v = dg.head(e);
			if ((--(nin[v])) == 0) q.addLast(v);
		}
	}
	return (i == dg.n());
}

KosarajuSCC::KosarajuSCC(Digraph& dg) {
	marked = new bool[dg.n()];
	for (int i = 0; i < dg.n(); i++)
		marked[i] = false;
	id = new int[dg.n()];
	count = 0;

	Digraph* dgR = dg.reverse();
	DepthFirstOrder* dforder = new DepthFirstOrder(*dgR);
	stack<int>& reverseOrder = dforder->reversePostOrder();
	delete dgR;

	while (!reverseOrder.empty()) {
		int v = reverseOrder.top();
		reverseOrder.pop();
		if (!marked[v]) {
			dfs(dg, v);
			count++;
		}
	}
	delete dforder;
}

main() {
	int i; vertex u,v; edge e; string s;
	Digraph dg; dg.read(cin);
	int *pos = new int[dg.n()+1];
	vertex *vert = new vertex[dg.n()+1];
	toposort(dg,pos,vert);
	Digraph inOrder(dg.n(),dg.m());
	cout << "# ";
	for (i = 1; i <= dg.n(); i++) {
		u = vert[i];
		cout << Util::node2string(u,dg.n(),s) << "->";
		cout << Util::node2string(pos[u],dg.n(),s) << " ";
		if ((i%10) == 0) cout << "\n# ";
		for (e = dg.firstOut(u); e != 0; e=dg.nextOut(u,e)) {
			v = dg.head(e);
			inOrder.join(pos[u],pos[v]); 
		}
	}
	inOrder.sortAdjLists();
	cout << endl << inOrder.toString(s);
}