Java Program to Check whether a Graph is 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;
```
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import java.util.Stack;
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```
 
```
```
public class BipartiteDfs
```
```
{
```
```
    private int numberOfVertices;
```
```
    private Stack<Integer> stack;
```
```
 
```

    public static final int NO_COLOR = 0;

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    public static final int RED = 1;
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    public static final int BLUE = 2;
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```
 
```

    public BipartiteDfs(int numberOfVertices)

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    {
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        this.numberOfVertices = numberOfVertices;

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        stack = new Stack<Integer>();
```
```
    }
```
```
 
```

    public boolean isBipartite(int adjacencyMartix[][], int source)

```
    {
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        int[] colored = new int[numberOfVertices + 1];

        for (int vertex = 1; vertex <= numberOfVertices; vertex++)

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        {
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```
            colored[vertex] = NO_COLOR;
```
```
        }
```
```
 
```
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        stack.push(source);
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        colored[source] = RED;
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        int element = source;
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        int neighbours = source;
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        while (!stack.empty())
```
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        {
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            element = stack.peek();
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            neighbours = element;
```

            while (neighbours <= numberOfVertices)

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            {
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                if (adjacencyMartix[element][neighbours] == 1&& colored[neighbours] == colored[element])

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                {
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                    return false;
```
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                }
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                if (adjacencyMartix[element][neighbours] == 1 && colored[neighbours] == NO_COLOR)

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                {
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                    colored[neighbours] = (colored[element] == RED) ? BLUE : RED;

                    stack.push(neighbours);

                    element = neighbours;

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                    neighbours = 1;
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                    continue;
```
```
                }
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                neighbours++;
```
```
            }
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            stack.pop();
```
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        }
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        return true;
```
```
    }
```
```
 
```

    public static void main(String... arg)

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    {
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        int number_of_nodes, source;
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        Scanner scanner = null;
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```
 
```
```
        try
```
```
        {
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            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++)

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            {
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                for (int j = 1; j <= number_of_nodes; j++)

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                {	
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                    adjacency_matrix[i][j] = scanner.nextInt();

```
                }
```
```
            }
```

            for (int i = 1; i <= number_of_nodes; i++)

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            {
```

                for (int j = 1; j <= number_of_nodes; j++)

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                {	
```

                    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");

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            source = scanner.nextInt();
```
```
 
```

            BipartiteDfs bipartiteDfs = new BipartiteDfs(number_of_nodes);

            if (bipartiteDfs.isBipartite(adjacency_matrix, source))

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            {
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                System.out.println("The given graph is bipartite");

```
            } else 
```
```
            {
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                System.out.println("The given graph is not bipartite");

```
            }
```

        } catch (InputMismatchException inputMismatch)

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        {
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            System.out.println("Wrong Input format");

```
        }
```
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        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

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