private void visit(EdgeWeightedGraph G, int v)
{
// Mark v and add to pq all edges from v to unmarked vertices.
marked[v] = true;
foreach (Edge e in G.Adj(v))
if (!marked[e.other(v)])
pq.Insert(e);
}
private IndexPriorityQueue<Double> pq; // eligible crossing edges
#endregion Fields
#region Constructors
public PrimMST(EdgeWeightedGraph G)
{
edgeTo = new Edge[G.V];
distTo = new double[G.V];
marked = new bool[G.V];
for (int v = 0; v < G.V; v++)
distTo[v] = Double.PositiveInfinity;
pq = new IndexPriorityQueue<double>(G.V);
distTo[0] = 0.0;
pq.Insert(0, 0.0); // Initialize pq with 0, weight 0.
while (!pq.isEmpty())
visit(G, pq.Del()); // Add closest vertex to tree.
}
static void Main(string[] args)
{
EdgeWeightedGraph ewg=new EdgeWeightedGraph(5);
ewg.Filling(5);
ewg.ShowEdges();
Console.WriteLine();
ewg.LazyPrimAlgr();
Console.WriteLine();
ewg.PrimAlgr();
Console.ReadKey();
}
private void visit(EdgeWeightedGraph G, int v)
{
// Add v to tree; update data structures.
marked[v] = true;
foreach (Edge e in G.Adj(v))
{
int w = e.other(v);
if (marked[w]) continue; // v-w is ineligible.
if (e.Weight < distTo[w])
{ // Edge e is new best connection from tree to w.
edgeTo[w] = e;
distTo[w] = e.Weight;
if (pq.contains(w)) pq.change(w, distTo[w]);
else pq.Insert(w, distTo[w]);
}
}
}
private PriorityQueue<Edge> pq; // crossing (and ineligible) edges
#endregion Fields
#region Constructors
public LazyPrimMST(EdgeWeightedGraph G)
{
pq = new PriorityQueue<Edge>(G.V);
marked = new bool[G.V];
mst = new Queue<Edge>();
visit(G, 0); // assumes G is connected (see Exercise 4.3.22)
while (!pq.isEmpty())
{
Edge e = pq.Del(); // Get lowest-weight
int v = e.either;
int w = e.other(v); // edge from pq.
if (marked[v] && marked[w])
continue; // Skip if ineligible.
mst.Enqueue(e); // Add edge to tree.
if (!marked[v])
visit(G, v); // Add vertex to tree
if (!marked[w])
visit(G, w); // (either v or w).
}
}
