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Home > Forums > Programmers > Languages > Java Forum

Need help creating edges between all vertices

thread269-1539361
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invalid6363 (Programmer)
26 Mar 09 22:43
I'm trying to create a graph with 'n' vertices and create edges between all the vertices.
Here is the code for adding vertices and edges:

CODE --> java

private static void setVertices(int n)
    {
        int vertexLength = n;
        
        /* Add vertices */
        for(int i = 0; i < vertexLength; i++)
        {
            undirGraph.addVertex("City" + String.valueOf(i+1) + " - ");
        }
    }

    private static void setEdges() {

        ListIterator<Vertex> i = vertices.listIterator();
        Object firstCity = i.next();
        Object nextCity = i.next();
        Object nextCity2 = i.next();

        /* Add edges between cities */
        while(i.hasNext())
        {
            nextCity2=i.next();
            nextCity = i.next();
            undirGraph.addEdge(firstCity, nextCity, (double)(Math.floor(Math.random()*10)+1));
            undirGraph.addEdge(nextCity, nextCity2, (double)(Math.floor(Math.random()*10)+2));
            
        }

    }

I get the following results:

CODE --> results

Enter number of vertices to be created (>=2):
5

First city to last city: City1 - City5 -
City5 -  City1 -  Total distance is 0.7778788292870616


Graph with 5 vertices and 2 edges.


Edges exist from the first vertex in each line to the other vertices in the line.
(Edge weights, if any, are given):

City1 -  City5 - 2.0
City2 -  
City3 -  
City4 -  
City5 -  City4 - 11.0

I'm able to create edges but i am not sure how to create edges between all of the vertices.
Can someone help me this problem?
Thank you.
 
Diancecht (Programmer)
27 Mar 09 3:18
The pseeucode would be something like

CODE

for i=1 to n
 for j=1 to i
  addEdge(element-j, element-i)

Cheers,
Dian

invalid6363 (Programmer)
28 Mar 09 1:37
Ok. Thanks.

new code to add edges between vertices:

CODE --> java

private static void setVertices(int n)
    {
        int vertexLength = n;
        
        /* Create vertices */
        for(int i = 0; i < vertexLength; i++)
        {
            undirGraph.addVertex("City" + String.valueOf(i+1) + " - ");
        }
    }

    private static void setEdges()
    {
        Object firstCity;
        Object nextCity;

        for (int g = 0; g < num;g++)
        {            
            ListIterator<Vertex> i = vertices.listIterator(g);
            firstCity = i.next();
            
            for(int h = 0;h < g;h++)
            {
                ListIterator<Vertex> j = vertices.listIterator(h);                
                nextCity = j.next();
                
                /* Create an edge between firstCity and nextCity + create a random weight */
                undirGraph.addEdge(firstCity, nextCity, (double)(Math.floor(Math.random()*10)+1));
                undirGraph.addEdge(nextCity, firstCity, (double)(Math.floor(Math.random()*10)+1));
            }
        }
        
    }

CODE --> results

Enter number of vertices to be created (>=2):
5

First city to last city: City1 - City5 -
City1 -  City2 -  City3 -  City4 -  City5 -  Total distance is 2.432884011676882


Graph with 5 vertices and 20 edges.


Edges exist from the first vertex in each line to the other vertices in the line.
(Edge weights, if any, are given):

City1 -  City2 - 10.0 City3 - 6.0 City4 - 1.0 City5 - 5.0
City2 -  City1 - 4.0 City3 - 10.0 City4 - 3.0 City5 - 10.0
City3 -  City1 - 8.0 City2 - 7.0 City4 - 8.0 City5 - 7.0
City4 -  City1 - 6.0 City2 - 5.0 City3 - 3.0 City5 - 7.0
City5 -  City1 - 2.0 City2 - 6.0 City3 - 9.0 City4 - 4.0

There is still one pair of vertices that do not have an edge between them. In a graph with 5 vertices, that would be between city2 and city5, but other than that it works great.
 
 
Diancecht (Programmer)
30 Mar 09 6:25
I'd not mix iterators and indexes.

[/code]
for (int i=0;i<vertices.length;i++)
 for (int j=0;j<i;j++)
   undirGraph.addEdge(vertices.get(i),vertices.get(j), (double)(Math.floor(Math.random()*10)+1));


[code]

Cheers,
Dian

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