Java Program to Check the Connectivity of Undirected Graph using DFS

This Java program,performs the DFS traversal on the given undirected graph represented by a adjacency matrix to check connectivity.the DFS traversal makes use of an stack.

Here is the source code of the Java program to check the connectivity of a undirected graph. 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.Scanner;
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import java.util.Stack;
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```
```
public class UndirectedConnectivityDfs
```
```
{
```
```
    private Stack<Integer> stack;
```
```
 
```
```
    public UndirectedConnectivityDfs() 
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    {
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        stack = new Stack<Integer>();
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    } 
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```
 
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    public void dfs(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 element = source;		
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        int i = source;	
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        visited[source] = 1;		
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        stack.push(source);
```
```
 
```
```
        while (!stack.isEmpty())
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        {
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            element = stack.peek();
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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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                    stack.push(i);
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                    visited[i] = 1;
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                    element = i;
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                    i = 1;
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	            continue;
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                }
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                i++;
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	    }
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            stack.pop();	
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        }
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        boolean connected = false;
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```
 
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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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```
 
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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_of_nodes, source;
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        Scanner scanner = null;
```
```
 	try
```
```
        {
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	    System.out.println("Enter the number of nodes in the graph");

            scanner = new Scanner(System.in);

            number_of_nodes = scanner.nextInt();

```
 
```

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

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

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

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

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

```
 
```

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

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            {
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                for (int j = 1; j <= number_of_nodes; j++)

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                {	
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                     if (adjacency_matrix[i][j] == 1 && adjacency_matrix[j][i] == 0)

```
                     {
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                         adjacency_matrix[j][i] = 1;

```
                     }
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```
                }
```
```
            }			
```
```
 
```

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

            source = scanner.nextInt();

```
 
```

            UndirectedConnectivityDfs undirectedConnectivity= new UndirectedConnectivityDfs();

            undirectedConnectivity.dfs(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();	
```
```
    }	
```
```
}
```

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

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