Java Program to Traverse a Graph using BFS

Code:

import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class BFS
{ 

    private Queue queue;

    public BFS()
    {
        queue = new LinkedList();
    }

    public void bfs(int adjacency_matrix[][], int source)
    {
        int number_of_nodes = adjacency_matrix[source].length - 1;

        int[] visited = new int[number_of_nodes + 1];
        int i, element;

        visited[source] = 1;
        queue.add(source);

        while (!queue.isEmpty())
        {
            element = queue.remove();
            i = element;
            System.out.print(i + "\t");
            while (i <= number_of_nodes)
            {
                if (adjacency_matrix[element][i] == 1 && visited[i] == 0)
                {
                    queue.add(i);
                    visited[i] = 1;
                }
                i++;
            }
        }
    }

    public static void main(String... arg)
    {
        int number_no_nodes, source;
        Scanner scanner = null;

        try
        {
            System.out.println("Enter the number of nodes in the graph");
            scanner = new Scanner(System.in);
            number_no_nodes = scanner.nextInt();

            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();

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

            System.out.println("The BFS traversal of the graph is ");
            BFS bfs = new BFS();
            bfs.bfs(adjacency_matrix, source);

        } catch (InputMismatchException inputMismatch)
        {
            System.out.println("Wrong Input Format");
        }
        scanner.close();
    }
}


Output:

Enter the number of nodes in the graph
4
Enter the adjacency matrix
0 1 0 1
0 0 1 0
0 1 0 1
0 0 0 1
Enter the source for the graph
1
The BFS traversal of the graph is 
1 2 4 3



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