Java Program to Check the Connectivity of Directed Graph using BFS

This Java program, to perform the bfs traversal of a given directed graph in the form of the adjacency matrix and check for the connectivity of the graph.the bfs traversal makes use of a queue.

Here is the source code of the Java program to check the connectivity of the directed graph using BFS. The Java program is successfully compiled and run on a Linux system. The program output is also shown below.

import java.util.InputMismatchException;

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import java.util.LinkedList;
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import java.util.Queue;
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import java.util.Scanner;
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public class DirectedConnectivityBFS
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{
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    private Queue<Integer> queue;
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```
 
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    public DirectedConnectivityBFS()
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    {
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        queue = new LinkedList<Integer>();

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    }
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```
 
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```
 
```
```
 
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    public void bfs(int adjacency_matrix[][], int source)

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    {
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        int number_of_nodes = adjacency_matrix[source].length - 1;

        int[] visited = new int[number_of_nodes + 1];

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        int i, element;
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        visited[source] = 1;
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        queue.add(source);
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        while (!queue.isEmpty())
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        {
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            element = queue.remove();
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            i = element;
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           while (i <= number_of_nodes)
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           {
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               if (adjacency_matrix[element][i] == 1 && visited[i] == 0)

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               {
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                   queue.add(i);
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                   visited[i] = 1;
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               }
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               i++;
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           }
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        }
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        boolean connected = false; 
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        for (int vertex = 1; vertex <= number_of_nodes; vertex++)

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        {
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            if (visited[vertex] == 1)
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            {
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                connected = true;
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            } else
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            { 
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                connected = false;
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                break;
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            }
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        }
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        if (connected)
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        {
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            System.out.println("The graph is connected");

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        } else
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        {
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            System.out.println("The graph is disconnected");

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        }
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    } 
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    public static void main(String... arg)

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    {
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        int number_no_nodes, source;
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        Scanner scanner = null;
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        try
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        {   
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            System.out.println("Enter the number of nodes in the graph");

            scanner = new Scanner(System.in);

            number_no_nodes = scanner.nextInt();

```
 
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            int adjacency_matrix[][] = new int[number_no_nodes + 1][number_no_nodes + 1];

            System.out.println("Enter the adjacency matrix");

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

                for (int j = 1; j <= number_no_nodes; j++)

                    adjacency_matrix[i][j] = scanner.nextInt();

```
 
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            System.out.println("Enter the source for the graph");

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            source = scanner.nextInt();
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            DirectedConnectivityBFS directedConnectivity= new DirectedConnectivityBFS();

            directedConnectivity.bfs(adjacency_matrix, source);

```
 
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        } catch (InputMismatchException inputMismatch)

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        {
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            System.out.println("Wrong Input Format");

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        }
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        scanner.close();
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    }
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}
```

$javac DirectedConnectivityBFS.java
$java DirectedConnectivityBFS
Enter the number of nodes in the graph
5
Enter the adjacency matrix
0 1 1 1 0
0 0 1 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
Enter the source for the graph
1
The graph is disconnected

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