Java Program to Implement Find all Cross Edges in a Graph

Code:

import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.Scanner;
import java.util.Set;
import java.util.Stack;

public class CrossEdge
{
    private Stack stack;
    private HashMap crossEdges;
    private int adjacencyMatrix[][];

    public CrossEdge() 
    {
        stack = new Stack();
        crossEdges = new HashMap();
    }

    public void dfs(int adjacency_matrix[][], int source)
    {
        int number_of_nodes = adjacency_matrix[source].length - 1;
        adjacencyMatrix = new int[number_of_nodes + 1][number_of_nodes + 1];
        for (int sourcevertex = 1; sourcevertex <= number_of_nodes; sourcevertex++)
        {
            for (int destinationvertex = 1; destinationvertex <= number_of_nodes; destinationvertex++)
            {
                adjacencyMatrix[sourcevertex][destinationvertex] = 
                     adjacency_matrix[sourcevertex][destinationvertex];
            }
        }

        int visited[] = new int[number_of_nodes + 1];
        int element = source;
        int destination = source;
        visited[source] = 1;
        stack.push(source);

        while (!stack.isEmpty())
        {
            element = stack.peek();
            destination = element;
    while (destination <= number_of_nodes)
    {
                if (adjacencyMatrix[element][destination] == 1 && visited[destination] == 1)
                {
                    if (!stack.contains(destination))
                    {
                        if ( element > destination )
                            crossEdges.put(element, destination);
                    }
                }

              if (adjacencyMatrix[element][destination] == 1 && visited[destination] == 0)
        {
                    stack.push(destination);
                    visited[destination] = 1;
                    adjacencyMatrix[element][destination] = 0;
                    element = destination;
                    destination = 1;
            continue;
                }
                destination++;
    }
            stack.pop();
        }
    }

    public void printCrossEdges()
    {
        System.out.println("\nSOURCE  : DESTINATION");
        Set source = crossEdges.keySet();
        for (Integer sourcevertex : source)
        {
            System.out.println(sourcevertex + "\t:\t"+ crossEdges.get(sourcevertex));
        }
    }

    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();


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

            CrossEdge crossEdge = new CrossEdge();
            crossEdge.dfs(adjacency_matrix, source);
            crossEdge.printCrossEdges();

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



Output:

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 1
0 0 1 0 0
Enter the source for the graph
1
The Cross Edges are
SOURCE  : DESTINATION
4 : 2
5 : 3



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