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 IEnumerable <IDirectedEdge> cycle; //edgeTo中是否含有负权重环
public BellmanFordSP(IEdgeWeightedDIgraph G, int s) : base(G, s)
{
onQ = new bool[G.V];
queue = new Chapter1.Queue <int>();
queue.Enqueue(s);
onQ[s] = true;
while (!queue.IsEmpty && !HasNegativeCycle())
{
int v = queue.Dequeue();
onQ[v] = false;
Relax(G, v);
}
}
public IEnumerable <IEdge> Edges()
{
var mst = new Chapter1.Queue <IEdge>();
for (int v = 0; v < edgeTo.Length; v++)
{
IEdge e = edgeTo[v];
if (e != null)
{
mst.Enqueue(e);
}
}
return(mst);
}
private void Bfs(IGraph g, int s)
{
var queue = new Chapter1.Queue <int>();
marked[s] = true; //起点被标记
queue.Enqueue(s);
while (!queue.IsEmpty)
{
int v = queue.Dequeue(); //从队列中删除一个顶点
foreach (int w in g.Adj(v))
{
if (!marked[w])
{
edgeTo[w] = v;
marked[w] = true;
queue.Enqueue(w);
}
}
}
}
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);
}
}
