[FIXED] How to efficiently access the information in an undirected unweighted graph?

Issue

I'm working on an assignment and I have a few problem. I implement a class Graph that can represent an un-weighted and undirected graph using Adjacency Lists. My method are for now addEdges and addVertex. The social network graph was given in an attached file (each line represents two nodes connected by an edge). I can already access the graph and see who is friend with who (please see the output). I want to find out, who have the most friend and how many friends people have on the average. How can I access this informations?

public class UndirectedGraphs {
HashMap<String, LinkedList<String>> socialNetworkAdj;

public UndirectedGraphs() {
    socialNetworkAdj = new HashMap<String, LinkedList<String>>();


}
public void addVertex(String label){
    socialNetworkAdj.put(label, new LinkedList<String>());
}

public LinkedList<String> getEdges(String label) {
    return socialNetworkAdj.get(label);
}

public void addEdges(String ver1, String ver2) {
    if (!socialNetworkAdj.containsKey(ver1)) {
        addVertex(ver1);
    }

    if (!socialNetworkAdj.containsKey(ver2)) {
        addVertex(ver2);
    }
    socialNetworkAdj.get(ver1).add(ver2);
    socialNetworkAdj.get(ver2).add(ver1);
    //System.out.println(socialNetworkAdj);

}


public static void main(String[] args) throws Exception {

    File filePath = new File("C:\\Users\\F\\Desktop\\A9\\social_network.txt");
    FileReader fr = new FileReader(filePath);
    BufferedReader br = new BufferedReader(fr);

    String[] tokens = new String[2];
    //ArrayList<String> nodes = new ArrayList<>();
    UndirectedGraphs graph = new UndirectedGraphs();
    String line;
    String var1 = tokens[0];
    String var2 = tokens[1];

    while ((line = br.readLine()) != null) {
        String[] nodes = line.split("\\s+");
        if (nodes.length == 2){
            graph.addEdges(nodes[0], nodes[1] );
        }

    }

    System.out.println("\nAnna: --> " + graph.getEdges("Anna"));
    System.out.println("\nMarie: --> " + graph.getEdges("Marie"));
    System.out.println("\nJakob: --> " + graph.getEdges("Jakob"));
    System.out.println("\nHanna: --> " + graph.getEdges("Hanna"));
    System.out.println("\nFelix: --> " + graph.getEdges("Felix"));
    System.out.println("\nEmma: --> " + graph.getEdges("Emma"));
    System.out.println("\nBen: --> " + graph.getEdges("Ben"));
    System.out.println("\nUlrike: --> " + graph.getEdges("Ulrike"));
    System.out.println("\nLutz: --> " + graph.getEdges("Lutz"));
    System.out.println("\nSofia: --> " + graph.getEdges("Sofia"));
    System.out.println("\nEmilia: --> " + graph.getEdges("Emilia"));
    System.out.println("\nMia: --> " + graph.getEdges("Mia"));
    br.close();

}

}

Output

Anna: --> [Noah, Marie]

Marie: --> [Anna, Noah, Jakob, Hanna]

Jakob: --> [Marie, Felix]

Hanna: --> [Marie, Felix, Jonas]

Felix: --> [Jakob, Hanna, Jonas, Emma, Finn, Ben]

Emma: --> [Felix, Finn]

Ben: --> [Felix, Finn, Lina]

Ulrike: --> [Wolfgang]

Lutz: --> [Stephan, Wolfgang]

Sofia: --> [Emilia]

Emilia: --> [Sofia, Luis, Mia]

Mia: --> [Emilia, Lukas]

Solution

Well you can try to find the length of the LinkedList for each node, something like this -

int total = 0; //variable to store total of friends in the graph
for (String person : graph.socialNetworkAdj.keySet()) 
{           
      int counter = socialNetworkAdj.get(person).size(); //find the length
      System.out.println(person+" has "+counter+ " friends.\n");
      total+= counter; 
}
System.out.println("Average friends : "+(float)total / graph.socialNetworkAdj.size()); //considering that the socialNetworkAdj is not empty

Answered By - LiavC

Answer Checked By - Pedro (PHPFixing Volunteer)