programming-examples/java/Searching_Sorting_Algorithms/Java Program to Represent Graph Using Incidence Matrix.java

/*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.*/

//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();
    }

}

/*
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