Java Program to Detect Cycle in a Graph using Topological Sort

This Java program,to perform the topological Sort on a given graph by the DFS method.The topological sort is performed on a directed acyclic graph.

Here is the source code of the Java program to check for cycle in topological sort. 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 TopoCycle
```
```
{
```
```
    private Stack<Integer> stack;
```
```
 
```
```
    public TopoCycle() 
```
```
    {
```
```
        stack = new Stack<Integer>();
```
```
    }
```
```
 
```

    public boolean checkCycle(int adjacency_matrix[][], int source)

```
    {
```

        int number_of_nodes = adjacency_matrix[source].length - 1;

        int[] topological_sort = new int [number_of_nodes + 1];

```
        int pos = 1;
```
```
        int j;
```
```
        boolean cycle = false;
```
```
 
```
```
 
```

        int visited[] = new int[number_of_nodes + 1];

```
        int element = source;
```
```
        int i = source;
```
```
        visited[source] = 1;
```
```
        stack.push(source);
```
```
 
```
```
 
```
```
        while (!stack.isEmpty())
```
```
        {
```
```
            element = stack.peek();
```

            while (i <= number_of_nodes)

```
            {
```

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

```
                {
```

                    if (stack.contains(i))

```
                    {
```

                        System.out.println("The Graph Contains a cycle");

```
                        cycle = true; 
```
```
                        return cycle;
```
```
                    }
```
```
                }
```

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

```
                {
```
```
                    stack.push(i);
```
```
                    visited[i] = 1;
```
```
                    element = i;
```
```
                    i = 1;
```
```
                    continue;
```
```
                }
```
```
                i++;
```
```
            }
```
```
            j = stack.pop();	
```

            topological_sort[pos++] = j;

```
            i = ++j;
```
```
        }
```

        System.out.println("The Graph does not Contain cycle");

```
        return cycle;
```
```
    }	
```
```
 
```

    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();
```
```
 
```

	    TopoCycle topoCycle = new TopoCycle();

            topoCycle.checkCycle(adjacency_matrix, source);

```
 
```

        }catch(InputMismatchException inputMismatch)

```
        {
```

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

```
        }
```
```
        scanner.close();
```
```
    }
```
```
}
```

$javac TopoCycle.java
$java TopoCycle
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 1
0 1 0 0 1
0 0 0 1 0 
Enter the source for the graph
1
The Graph contains a cycle

Sanfoundry Global Education & Learning Series – 1000 Java Programs.

If you wish to look at all Java Programming examples, go to Java Programs.

If you find any mistake above, kindly email to [email protected]

« Prev - Java Program to Traverse a Graph using BFS

» Next - Java Program to Check the Connectivity of Undirected Graph using BFS

Related Posts:

Recommended Articles: