private void Dfs(EdgeWeightedDigraph G, int v) // v is start vertex here
{
onStack[v] = true;
marked[v] = true;
foreach (DirectedEdge e in G.GetAdj(v))
{
int w = e.To();
// short circuit if directed cycle found
if (cycle != null)
{
return;
}
// found new vertex, so recur
else if (!marked[w])
{
edgeTo[w] = v;
Dfs(G, w);
}
// trace back directed cycle
else if (onStack[w])
{
cycle = new Stack <int>();
for (int x = v; x != w; x = edgeTo[x])
{
cycle.Push(x);
}
cycle.Push(w);
cycle.Push(v);
// Debug.Assert(Check());
}
}
onStack[v] = false;
}
public DijkstraSP(EdgeWeightedDigraph G, int s)
{
foreach (DirectedEdge e in G.GetEdges())
{
if (e.GetWeight() < 0)
{
throw new ArgumentException("Negative weight");
}
}
distTo = new double[G.GetVertices()];
edgeTo = new DirectedEdge[G.GetVertices()];
ValidateVertex(s);
for (int v = 0; v < G.GetVertices(); v++)
{
distTo[v] = double.PositiveInfinity;
}
distTo[s] = 0.0;
// relax vertices in order of distance from s
Comparer <double> comparer = Comparer <double> .Default;
pq = new IndexMinPQ <Double>(G.GetVertices(), comparer);
pq.Insert(s, distTo[s]);
while (!pq.IsEmpty())
{
pq.DelMin(out int index, out double key);
int v = index;
foreach (DirectedEdge e in G.GetAdj(v))
{
Relax(e);
}
}
}
// relax vertex v and put other endpoints on queue if changed
private void Relax(EdgeWeightedDigraph G, int v)
{
//for (DirectedEdge e : G.adj(v))
foreach (DirectedEdge e in G.GetAdj(v))
{
int w = e.To();
if (distTo[w] > distTo[v] + e.GetWeight())
{
distTo[w] = distTo[v] + e.GetWeight();
edgeTo[w] = e;
if (!onQueue[w])
{
queue.Enqueue(w);
onQueue[w] = true;
}
}
if (cost++ % G.GetVertices() == 0)
{
FindNegativeCycle();
if (IsNegativeCycle())
{
return; // found a negative cycle
}
}
}
}
private void Dfs(EdgeWeightedDigraph G, int v)
{
marked[v] = true;
Pre.Enqueue(v);
foreach (DirectedEdge e in G.GetAdj(v))
{
int w = e.To();
if (!marked[w])
{
Dfs(G, w);
}
}
Post.Enqueue(v);
ReversePost.Push(v);
}
// check that algorithm computes either the topological order or finds a directed cycle
private void Dfs(EdgeWeightedDigraph G, int v)
{
onStack[v] = true;
marked[v] = true;
foreach (DirectedEdge e in G.GetAdj(v))
{
int w = e.To();
// short circuit if directed cycle found
if (cycle != null)
{
return;
}
// found new vertex, so recur
else if (!marked[w])
{
edgeTo[w] = e;
Dfs(G, w);
}
// trace back directed cycle
else if (onStack[w])
{
cycle = new Stack <DirectedEdge>();
DirectedEdge f = e;
while (f.From() != w)
{
cycle.Push(f);
f = edgeTo[f.From()];
}
cycle.Push(f);
return;
}
}
onStack[v] = false;
}
public AcyclicSP(EdgeWeightedDigraph G, int s)
{
distTo = new double[G.GetVertices()];
edgeTo = new DirectedEdge[G.GetVertices()];
for (int v = 0; v < G.GetVertices(); v++)
{
distTo[v] = Double.PositiveInfinity;
}
distTo[s] = 0.0;
ValidateVertex(s);
Topological topological = new Topological(G);
if (!topological.IsOrder())
{
throw new ArgumentException("Digraph is not acyclic.");
}
foreach (int v in topological.ReversePost)
{
foreach (DirectedEdge e in G.GetAdj(v))
{
Relax(e);
}
}
}