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import java.util.ArrayList;
public class PrimsAlgorithm
{
public static boolean added[];
public static ArrayList<Edge> mst;
public static IndexedPriorityQueue<Integer> pq;
public static int cost[];
public static int fromVertex[];
public static void primsMST(WeightedGraph G)
{
added=new boolean[G.V];
mst=new ArrayList<Edge>();
pq=new IndexedPriorityQueue<Integer>(G.V);
cost=new int[G.V];
fromVertex=new int[G.V];
for(int i=0;i<G.V;i++)
cost[i]=Integer.MAX_VALUE;
cost[0]=0;
pq.insert(0,0);
while(pq.isEmpty()==false)
{
int min=pq.delMin();
Edge e=new Edge(min,fromVertex[min],cost[min]);
mst.add(e);
visit(G,min);
}
printPrims(G.V);
}
public static void visit(WeightedGraph G, int v)
{
added[v]=true;
int len=G.adj.get(v).size();
for(int i=0;i<len;i++)
{
Edge e=G.adj.get(v).get(i);
if(added[e.otherEnd(v)]==false)
{
if(e.weight<cost[e.otherEnd(v)])
{
cost[e.otherEnd(v)]=e.weight;
fromVertex[e.otherEnd(v)]=v;
if(pq.contains(e.otherEnd(v)))
pq.changeKey(e.otherEnd(v), e.weight);
else
pq.insert(e.otherEnd(v), e.weight);
}
}
}
}
public static void printPrims(int v)
{
int len=mst.size();
System.out.println("Edges with their weights in mst:");
for(int i=1;i<len;i++)
{
Edge e=mst.get(i);
System.out.println(e.end1+" "+e.end2+" "+e.weight);
}
}
public static void main(String[] args)
{
WeightedGraph G=new WeightedGraph();
primsMST(G);
}
}
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