public LazyPrimMST(IEdgeWeightGraph g)
{
pq = new MinPQ <IEdge>();
marked = new bool[g.V];
mst = new Chapter1.Queue <IEdge>();
Visit(g, 0);//假设G是联通的
while (!pq.IsEmpty)
{
IEdge e = pq.Delete(); //找到权重最小的边
int v = e.Either;
int w = e.Other(v);
if (marked[v] && marked[w]) //跳过失效的边
{
continue;
}
mst.Enqueue(e); //将边添加到树中
if (!marked[v])
{
Visit(g, v);
}
if (!marked[w])
{
Visit(g, w);
}
}
}
private void Visit(IEdgeWeightGraph g, int v)
{
marked[v] = true;
foreach (var e in g.Adj(v))
{
int w = e.Other(v);
if (marked[w])
{
continue;
}
if (e.Weight < distTo[w]) //更新最佳的边
{
edgeTo[w] = e;
distTo[w] = e.Weight;
if (pq.Contains(w))
{
pq.ChangeKey(w, distTo[w]);
}
else
{
pq.Insert(w, distTo[w]);
}
}
}
}
private static void ShowMSTResult(IEdgeWeightGraph G, IMST mst)
{
//StdOut.Println(G.ToString());
foreach (var edge in mst.Edges())
{
StdOut.Println(edge);
}
StdOut.Println(mst.Weight);
}
private void Visit(IEdgeWeightGraph g, int v)
{
//标记顶点v并将所有链接v和未被标记的顶点加入pq
marked[v] = true;
foreach (var edge in g.Adj(v))
{
if (!marked[edge.Other(v)])
{
pq.Insert(edge);
}
}
}
private IndexMinPQ <double> pq; //有效的横切边
public PrimeMST(IEdgeWeightGraph 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 IndexMinPQ <double>(G.V);
distTo[0] = 0.0;
pq.Insert(0, 0.0); //顶点0权重初始化
while (!pq.IsEmpty)
{
Visit(G, pq.DeleteMin());
}
}
public KruskalMST(IEdgeWeightGraph G)
{
mst = new Chapter1.Queue <IEdge>();
MinPQ <IEdge> pq = new MinPQ <IEdge>();
foreach (var e in G.Edges())
{
pq.Insert(e);
}
UF uf = new UF(G.V);
while (!pq.IsEmpty && mst.Size < G.V - 1)
{
IEdge e = pq.Delete(); //找到权重最小的边
int v = e.Either, w = e.Other(v);
if (uf.Connected(v, w)) //忽略失效的边
{
continue;
}
uf.Union(v, w);
mst.Enqueue(e);
}
}
