public void TestDigraph()
{
Random rand = new Random();
int v = rand.Next(10, 30);
Digraph g = new Digraph(v);
int e0 = rand.Next(10, 30);
string strs = string.Empty;
for (int i = 0; i < e0; i++)
{
int v1 = rand.Next(0, v);
int v2 = rand.Next(0, v);
string str = v1 + " - " + v2 + ",";
string str1 = v2 + " - " + v1 + ",";
if (v1 == v2 || strs.Contains(str) || strs.Contains(str1))
{
i--;
continue;
}
g.AddEdge(v1, v2);
strs += str;
}
Debug.WriteLine("input e: " + strs);
Debug.WriteLine(g.ToString());
Digraph g1 = new Digraph(g);
Debug.WriteLine("g1: ");
Debug.WriteLine(g1.ToString());
}
/// <summary>
/// check that algorithm computes either the topological order or finds a directed this.Cycle
/// </summary>
/// <param name="g"></param>
/// <param name="v"></param>
private void dfs(Digraph g, int v)
{
this._onStack[v] = true;
this._marked[v] = true;
foreach (int w in g.Adj[v])
if (this.Cycle != null)
{
// short circuit if directed this.Cycle found
return;
}
else if (!this._marked[w])
{
//found new vertex, so recur
this._edgeTo[w] = v;
this.dfs(g, w);
}
else if (this._onStack[w])
{
// trace back directed this.Cycle
this.Cycle = new Stack<int>();
for (int x = v; x != w; x = this._edgeTo[x])
this.Cycle.Push(x);
this.Cycle.Push(w);
this.Cycle.Push(v);
}
this._onStack[v] = false;
}
/// <summary>
/// Computes the vertices in digraph G that are to any of the source vertices sources.
/// </summary>
/// <param name="g"></param>
/// <param name="sources"></param>
public DirectedDFS(Digraph g, IEnumerable<int> sources)
{
this.Marked = new bool[g.V];
foreach (int v in sources)
if (!this.Marked[v])
this.dfs(g, v);
}
public Digraph Reverse()
{
Digraph r = new Digraph(V);
for (int v = 0; v < V; v++)
foreach (int w in this.Adj[v])
r.AddEdge(w, v);
return r;
}
private void dfs(Digraph g, int v)
{
this.Marked[v] = true;
this.ID[v] = this.Count;
foreach (int w in g.Adj[v])
if (!this.Marked[w])
this.dfs(g, w);
}
public Topological(Digraph g)
{
DirectedCycle cycleFinder = new DirectedCycle(g);
if (!cycleFinder.HasCycle())
{
DepthFirstOrder dfs = new DepthFirstOrder(g);
this.Order = dfs.ReversePost;
}
}
/// <summary>
/// Determines whether the digraph G has a directed this.Cycle and, if so, finds such a this.Cycle
/// </summary>
/// <param name="g"></param>
public DirectedCycle(Digraph g)
{
this._marked = new bool[g.V];
this._onStack = new bool[g.V];
this._edgeTo = new int[g.V];
for (int v = 0; v < g.V; v++)
if (!this._marked[v] && this.Cycle == null)
this.dfs(g, v);
}
public DepthFirstOrder(Digraph g)
{
this.Pre = new Queue<int>();
this.Post = new Queue<int>();
this.ReversePost = new Stack<int>();
this._marked = new bool[g.V];
for (int v = 0; v < g.V; v++)
if (!this._marked[v])
this.dfs(g, v);
}
private void dfs(Digraph g, int v)
{
this.Pre.Enqueue(v);
this._marked[v] = true;
foreach (int w in g.Adj[v])
if (!this._marked[w])
this.dfs(g, w);
this.Post.Enqueue(v);
this.ReversePost.Push(v);
}
public Digraph(Digraph g)
: this(g.V)
{
this.E = g.E;
for (int v = 0; v < g.V; v++)
{
Part1.Stack<int> reverse = new Part1.Stack<int>();
foreach (int w in g.Adj[v])
reverse.Push(w);
foreach (int w in reverse)
this.Adj[v].Add(w);
}
}
/// <summary>
/// Computes the connected components of the directed graph G.
/// </summary>
/// <param name="g"></param>
public KosarajuSCC(Digraph g)
{
this.Marked = new bool[g.V];
this.ID = new int[g.V];
DepthFirstOrder order = new DepthFirstOrder(g.Reverse());
foreach (int v in order.ReversePost)
if (!this.Marked[v])
{
this.dfs(g, v);
this.Count++;
}
}
public void TestDirectedCycle()
{
Digraph g = new Digraph(6);
g.AddEdge(0, 5);
g.AddEdge(5, 4);
g.AddEdge(4, 3);
g.AddEdge(3, 5);
g.AddEdge(0, 1);
g.AddEdge(1, 2);
g.AddEdge(2, 3);
Debug.WriteLine(g.ToString());
DirectedCycle finder = new DirectedCycle(g);
if (finder.HasCycle())
{
Debug.WriteLine("Directed cycle:");
foreach (var v in finder.Cycle)
Debug.Write(" => " + v);
}
else
Debug.WriteLine("No directed cycle!");
}
public void TestKosarajuSCCHasNotCycle()
{
Digraph g = new Digraph(6);
g.AddEdge(0, 1);
g.AddEdge(1, 2);
g.AddEdge(2, 3);
g.AddEdge(0, 4);
g.AddEdge(4, 5);
Debug.WriteLine(g.ToString());
DepthFirstOrder dfs = new DepthFirstOrder(g);
StringBuilder sb = new StringBuilder();
foreach (var item in dfs.ReversePost)
sb.Append(item + " ");
Debug.WriteLine(sb.ToString());
KosarajuSCC scc = new KosarajuSCC(g);
sb.Clear();
for (int i = 0; i < scc.ID.Length; i++)
sb.Append(i + " - " + scc.ID[i] + Environment.NewLine);
Debug.WriteLine(sb.ToString());
}
/// <summary>
/// Computes the vertices in digraph G that are reachable from the source vertex s.
/// </summary>
/// <param name="g"></param>
/// <param name="s"></param>
public DirectedDFS(Digraph g, int s)
{
this.Marked = new bool[g.V];
this.dfs(g, s);
}
public TransitiveClosure(Digraph g)
{
this._all = new DirectedDFS[g.V];
for (int v = 0; v < g.V; v++)
this._all[v] = new DirectedDFS(g, v);
}