Question

For my BFS in JAVA in How can I get the output of this to be correct when I put in this adjacency matrix.

0 1 0 0 1 1 0 0
1 0 0 0 0 1 1 0
0 0 0 1 0 0 1 0
0 0 1 0 0 0 0 1
1 0 0 0 0 1 0 0
1 1 0 0 1 0 0 0
0 1 1 0 0 0 0 1
0 0 0 1 0 0 1 0

The output should be:

The BFS traversal of the graph is

1 2 6 8 3 4 5 7

Tree edges

0 1 0 0 1 1 0 0

0 0 0 0 0 0 1 0

0 0 0 1 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 1 0 0 0 0 1

0 0 0 0 0 0 0 0

Cross edges

0 0 0 0 0 0 0 0

0 0 0 0 0 1 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 1 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 1 0 0 0 0

The number of connected components is : 1

My code is as follows

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();

        }

    }

Answer 1

I guess the correct output should be 1 2 5 6 7 3 8 4

I have modified the method bfs()

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 = 1;

                System.out.print(element+ "\t");

                while (i <= number_of_nodes)

                {

                    if (adjacency_matrix[element][i] == 1 && visited[i] == 0)

                    {

                        queue.add(i);

                        visited[i] = 1;

                    }

                    i++;

                }

            }

        }