/// <summary>
/// Determines whether the edge-weighted digraph <c>G</c> has a
/// topological order and, if so, finds such a topological order.</summary>
/// <param name="G">the digraph</param>
///
public TopologicalX(EdgeWeightedDigraph G)
{
// indegrees of remaining vertices
int[] indegree = new int[G.V];
for (int v = 0; v < G.V; v++)
{
indegree[v] = G.Indegree(v);
}
// initialize
rank = new int[G.V];
order = new LinkedQueue <int>();
int count = 0;
// initialize queue to contain all vertices with indegree = 0
LinkedQueue <int> queue = new LinkedQueue <int>();
for (int v = 0; v < G.V; v++)
{
if (indegree[v] == 0)
{
queue.Enqueue(v);
}
}
for (int j = 0; !queue.IsEmpty; j++)
{
int v = queue.Dequeue();
order.Enqueue(v);
rank[v] = count++;
foreach (DirectedEdge e in G.Adj(v))
{
int w = e.To;
indegree[w]--;
if (indegree[w] == 0)
{
queue.Enqueue(w);
}
}
}
// there is a directed cycle in subgraph of vertices with indegree >= 1.
if (count != G.V)
{
order = null;
}
Debug.Assert(check(G));
}
/// <summary>
/// Initializes a new edge-weighted digraph that is a deep copy of <c>G</c>.</summary>
/// <param name="G">the edge-weighted digraph to copy</param>
///
public EdgeWeightedDigraph(EdgeWeightedDigraph G) : this(G.V)
{
numEdges = G.E;
for (int v = 0; v < G.V; v++)
{
indegree[v] = G.Indegree(v);
}
for (int v = 0; v < G.V; v++)
{
// reverse so that adjacency list is in same order as original
Stack <DirectedEdge> reverse = new Stack <DirectedEdge>();
foreach (DirectedEdge e in G.adj[v])
{
reverse.Push(e);
}
foreach (DirectedEdge e in reverse)
{
adj[v].Add(e);
}
}
}
