Java Program to Check whether Undirected Graph is Connected 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;
import java.util.Scanner;
import java.util.Stack;
 
public class UndirectedConnectivityDfs
{
    private Stack<Integer> stack;
 
    public UndirectedConnectivityDfs() 
    {
        stack = new Stack<Integer>();
    } 
 
    public void dfs(int adjacency_matrix[][], int source)
    {
        int number_of_nodes = adjacency_matrix.length - 1;	
        int visited[] = new int[number_of_nodes + 1];		
        int element = source;		
        int i = source;	
        visited = 1;		
        stack.push(source);
 
        while (!stack.isEmpty())
        {
            element = stack.peek();
            i = element;	
	    while (i <= number_of_nodes)
	    {
     	        if (adjacency_matrix[element][i] == 1 && visited[i] == 0)
	        {
                    stack.push(i);
                    visited[i] = 1;
                    element = i;
                    i = 1;
	            continue;
                }
                i++;
	    }
            stack.pop();	
        }
        boolean connected = false;
 
        for (int vertex = 1; vertex <= number_of_nodes; vertex++)
        {
            if (visited[vertex] == 1) 
            {
                connected = true;
            } else
            {
                connected = false;
                break;
            }
        }
 
        if (connected)
        {
            System.out.println("The graph is connected");
	}else
        {
            System.out.println("The graph is disconnected");
        }
    }
 
    public static void main(String...arg)
    {
        int number_of_nodes, source;
        Scanner scanner = null;
 	try
        {
	    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++)
            {
                for (int j = 1; j <= number_of_nodes; j++)
                {	
                     if (adjacency_matrix[i][j] == 1 && adjacency_matrix[j][i] == 0)
                     {
                         adjacency_matrix[j][i] = 1;
                     }
                }
            }			
 
	    System.out.println("Enter the source for the graph");
            source = scanner.nextInt(); 
 
            UndirectedConnectivityDfs undirectedConnectivity= new UndirectedConnectivityDfs();
            undirectedConnectivity.dfs(adjacency_matrix, source);	
 
        }catch(InputMismatchException inputMismatch)
        {
            System.out.println("Wrong Input format");
        }	
        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