Java Program to Check whether Graph is a Bipartite using DFS

This Java program is to check whether graph is bipartite using dfs. In the mathematical field of graph theory, a bipartite graph (or bigraph) is a graph whose vertices can be divided into two disjoint sets and such that every edge connects a vertex in to one in that is, and are each independent sets. Equivalently, a bipartite graph is a graph that does not contain any odd-length cycles.

Here is the source code of the Java program to check whether a graph is biparite using dfs. 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 BipartiteDfs
{
    private int numberOfVertices;
    private Stack<Integer> stack;
 
    public static final int NO_COLOR = 0;
    public static final int RED = 1;
    public static final int BLUE = 2;
 
    public BipartiteDfs(int numberOfVertices)
    {
        this.numberOfVertices = numberOfVertices;
        stack = new Stack<Integer>();
    }
 
    public boolean isBipartite(int adjacencyMartix[][], int source)
    {
        int[] colored = new int[numberOfVertices + 1];
        for (int vertex = 1; vertex <= numberOfVertices; vertex++)
        {
            colored[vertex] = NO_COLOR;
        }
 
        stack.push(source);
        colored = RED;
        int element = source;
        int neighbours = source;
        while (!stack.empty())
        {
            element = stack.peek();
            neighbours = element;
            while (neighbours <= numberOfVertices)
            {
                if (adjacencyMartix[element][neighbours] == 1&& colored[neighbours] == colored[element])
                {
                    return false;
                }
                if (adjacencyMartix[element][neighbours] == 1 && colored[neighbours] == NO_COLOR)
                {
                    colored[neighbours] = (colored[element] == RED) ? BLUE : RED;
                    stack.push(neighbours);
                    element = neighbours;
                    neighbours = 1;
                    continue;
                }
                neighbours++;
            }
            stack.pop();
        }
        return true;
    }
 
    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();
 
            BipartiteDfs bipartiteDfs = new BipartiteDfs(number_of_nodes);
            if (bipartiteDfs.isBipartite(adjacency_matrix, source))
            {
                System.out.println("The given graph is bipartite");
            } else 
            {
                System.out.println("The given graph is not bipartite");
            }
        } catch (InputMismatchException inputMismatch)
        {
            System.out.println("Wrong Input format");
        }
        scanner.close();
    }
}

$javac BipartiteBfs.java
$java BipartiteBfs
Enter the number of nodes in the graph
4
Enter the adjacency matrix
0 1 0 1
1 0 1 0
0 1 0 1
1 0 1 0
Enter the source for the graph
1
The given graph is bipartite