Java Program to Represent Graph Using Incidence Matrix

This is a java program to represent graph as a incidence list. The incidence matrix of G is a n × m matrix (b_{ij}), where n and m are the numbers of vertices and edges respectively, such that b_{ij} = 1 if the vertex v_i and edge x_j are incident and 0 otherwise.

Here is the source code of the Java Program to Represent Graph Using Incidence Matrix. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

//This is a java program to represent graph as a incidence matrix
import java.util.Scanner;
 
public class Represent_Graph_Incidence_Matrix 
{
    private final int rows;
    private final int cols;
    private int[][] incidence_matrix;
 
    public Represent_Graph_Incidence_Matrix(int v, int e) 
    {
        rows = v;
        cols = e;
        incidence_matrix = new int[rows + 1][cols + 1];
    }
 
    public void makeEdge(int to, int from, int edge, int edge_number) 
    {
        try 
        {
            incidence_matrix[to][edge_number] = edge;
            incidence_matrix[from][edge_number] = edge;
        }
        catch (ArrayIndexOutOfBoundsException index) 
        {
            System.out.println("The vertices does not exists");
        }
    }
 
    public int getEdge(int edge_number, int v) 
    {
        try 
        {
            return incidence_matrix[edge_number][v];
        }
        catch (ArrayIndexOutOfBoundsException index) 
        {
            System.out.println("The vertices does not exists");
        }
        return -1;
    }
 
    public static void main(String args[]) 
    {
        int v, e, count = 1, to = 0, from = 0, edge_number;
        Scanner sc = new Scanner(System.in);
        Represent_Graph_Incidence_Matrix graph;
        try 
        {
            System.out.println("Enter the number of vertices: ");
            v = sc.nextInt();
            System.out.println("Enter the number of edges: ");
            e = sc.nextInt();
 
            graph = new Represent_Graph_Incidence_Matrix(v, e);
 
            System.out.println("Enter the edges: <edge_number> <to> <from>");
            while (count <= e) 
            {
                edge_number = sc.nextInt();
                to = sc.nextInt();
                from = sc.nextInt();
 
                graph.makeEdge(to, from, 1, edge_number);
                count++;
            }
 
            System.out.println("The incidence matrix for the given graph is: ");
            System.out.print("  ");
            for (int i = 1; i <= v; i++)
                System.out.print(i + " ");
            System.out.println();
 
            for (int i = 1; i <= v; i++) 
            {
                System.out.print(i + " ");
                for (int j = 1; j <= v; j++) 
                    System.out.print(graph.getEdge(i, j) + " ");
                System.out.println();
            }
 
        }
        catch (Exception E) 
        {
            System.out.println("Somthing went wrong");
        }
 
        sc.close();
    }
 
}

Output:

$ javac Represent_Graph_Incidence_Matrix.java
$ java Represent_Graph_Incidence_Matrix
 
Enter the number of vertices: 
4 
Enter the number of edges: 
5
Enter the edges: <edge_number> <to> <from>
1 1 2
2 2 3
3 3 4 
4 4 1
1 1 3
The incidence matrix for the given graph is: 
  1 2 3 4 
1 1 0 0 1 
2 1 1 0 0 
3 1 1 1 0 
4 0 0 1 1