Graph Representation using Incidence Matrix in 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.

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;
```
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```

public class Represent_Graph_Incidence_Matrix

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{
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```
    private final int rows;
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```
    private final int cols;
```
```
    private int[][] incidence_matrix;
```
```
 
```

    public Represent_Graph_Incidence_Matrix(int v, int e)

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    {
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        rows = v;
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        cols = e;
```

        incidence_matrix = new int[rows + 1][cols + 1];

```
    }
```
```
 
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    public void makeEdge(int to, int from, int edge, int edge_number)

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    {
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        try 
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```
        {
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            incidence_matrix[to][edge_number] = edge;

            incidence_matrix[from][edge_number] = edge;

```
        }
```

        catch (ArrayIndexOutOfBoundsException index)

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        {
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            System.out.println("The vertices does not exists");

```
        }
```
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    }
```
```
 
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    public int getEdge(int edge_number, int v)

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    {
```
```
        try 
```
```
        {
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            return incidence_matrix[edge_number][v];

```
        }
```

        catch (ArrayIndexOutOfBoundsException index)

```
        {
```

            System.out.println("The vertices does not exists");

```
        }
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        return -1;
```
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    }
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```
 
```

    public static void main(String args[])

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    {
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        int v, e, count = 1, to = 0, from = 0, edge_number;

        Scanner sc = new Scanner(System.in);

        Represent_Graph_Incidence_Matrix graph;

```
        try 
```
```
        {
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            System.out.println("Enter the number of vertices: ");

```
            v = sc.nextInt();
```

            System.out.println("Enter the number of edges: ");

```
            e = sc.nextInt();
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```
 
```

            graph = new Represent_Graph_Incidence_Matrix(v, e);

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            System.out.println("Enter the edges: <edge_number> <to> <from>");

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            while (count <= e) 
```
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            {
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                edge_number = sc.nextInt();

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                to = sc.nextInt();
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                from = sc.nextInt();
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                graph.makeEdge(to, from, 1, edge_number);

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                count++;
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            }
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```
 
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            System.out.println("The incidence matrix for the given graph is: ");

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            System.out.print("  ");
```

            for (int i = 1; i <= v; i++)

                System.out.print(i + " ");

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            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) 
```
```
        {
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            System.out.println("Somthing went wrong");

```
        }
```
```
 
```
```
        sc.close();
```
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    }
```
```
 
```
```
}
```

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

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