创建一个扩展Graph类的二部图。 需要一些指导

Question

Looking for a step in the right direction. I have with me 4 classes that I have made. One is the super class which is graph and 3 subclasses called Edge, DirectedGraph, and BipartiteGraph.

I am having some trouble with creating a bipartite graph. Specifically I am given these directions:

Extend the Graph class to create a new BipartiteGraph class. It should inherit all the functionality of the super class:

• Automatically designate all even-index vertices (0,2,4) as part of the "A partition" from class and all odd-index vertices (1,3,5) as part of the "B partition". This requires no new code, just a conceptual expectation.

• Override the constructor for Graph to have the same input (number of vertices), call the super constructor, and then verify the graph is bipartite. That is, make sure that all existing edges are from a vertex in A to a vertex in B. If the graph is not bipartite, wipe out the internal representation (eg, for an adjacency matrix, make a size 0x0 array) so it cannot be used!

• Add a method setPreferences() that takes as a parameter an integer and an array or ArrayList of integers. The first integer is the vertex we want to attach preferences to and the list is that list of preferences, from most to least preferred. Verify that the array of ints contains all the members of the other partition in some order then save that information (you will need a 1-D array of arrays/ArrayLists to store these lists, one per vertex).

• Add the method stableMatching that has no parameters and returns a stable matching (in the form of an ArrayList of Pairs of ints). It will be helpful to consult Wikipedia: http://en.wikipedia.org/wiki/Stable_marriage_problem . As a start, I suggest verifying that each vertex has a preference list set for it!

Here is my constructor in the super class:

public class Graph {

// Setup privately modified variables which will define the graph

// These two parameters are storage variables for edges and vertices
// These variables were changed from Vertex and Edge to numVertices and
// numEdges.
private int numVertices;
private int numEdges;

// This will be the adjacency matrix to represent our graph, this will
// represent edges.
// adj_Matrix_Edges was previously static meaning it did not have access to
// multiple graphs, onyl one graph.
protected boolean[][] adj_Matrix_Edges;

// first step will be to setup the graph, using this constructor
public Graph(int vertices) {

    numVertices = vertices;

    if (numVertices < 0) {
        throw new RuntimeException(
                "Number of vertices cannot be a nonnegative value");
    }

    System.out.println("There are now " + numVertices
            + " vertices in the graph.");

    // A graph is created based on the specifications, N X N or (n^2)
    // graph.
    adj_Matrix_Edges = new boolean[vertices][vertices];
    }

And here is what I have so far for the BipartiteGraph class:

    public class BipartiteGraph extends Graph{

//Initialize two partitions for bipartite graph.
boolean[][] a;
boolean[][] b;


//Constructor of BipartiteGraph class
public BipartiteGraph(int vertices) {
    super(vertices);

    //Copy over even elements of graph into partition A.
    for (int i = 0; i < adj_Matrix_Edges.length; i++){
        for (int j = 0; j < adj_Matrix_Edges[i].length; j++){
            if (j%2 == 0){
                adj_Matrix_Edges[j] = a[j];
            }
        }
    }

    //Copy over odd elements of graph into Partition B.
    for (int i = 0; i < adj_Matrix_Edges.length; i++){
        for (int j = 0; j < adj_Matrix_Edges[i].length; j++){
            if (j%2 != 0){
                adj_Matrix_Edges[j] = b[j];
            }
        }
    }

}


public void setPreferences(int vertex, int[] preferences){

    if ()

}

public List stableMatching(){
    java.util.List<Integer> matching = new ArrayList<Integer>();


}

Am I making things too complicated, is the code simpler than it seems?

Answer 1

I think there is a mistake in the declaration of BipartiteGraph :

public class BipartiteGraph extends Graph{

boolean[][] a;
boolean[][] b;

You declare a and b as two dimensional arrays that is as matrices. a and b models complementary subsets of the set of vertices. Therefore, they should be either a list of vertices or an array of boolean which says if the ith vertex is in a . Also you don't need to store both since one is the complementary to the other.

Answer 2

maybe I missed something, but do you have to write this as homework? otherwise, you could rely on JUNG and use HyperGraph:

http://jung.sourceforge.net/doc/api/edu/uci/ics/jung/graph/Hypergraph.html