DirectedCycle (Algorithms 4/e)

Object
- edu.princeton.cs.algs4.DirectedCycle

```
public class DirectedCycle
extends Object
```
The DirectedCycle class represents a data type for determining whether a digraph has a directed cycle. The hasCycle operation determines whether the digraph has a simple directed cycle and, if so, the cycle operation returns one.
This implementation uses depth-first search. The constructor takes Θ(V + E) time in the worst case, where V is the number of vertices and E is the number of edges. Each instance method takes Θ(1) time. It uses Θ(V) extra space (not including the digraph).
See Topological to compute a topological order if the digraph is acyclic.
For additional documentation, see Section 4.2 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors
Constructor and Description

DirectedCycle(Digraph G)
Determines whether the digraph G has a directed cycle and, if so, finds such a cycle.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Iterable<Integer>`	`cycle()` Returns a directed cycle if the digraph has a directed cycle, and `null` otherwise.
`boolean`	`hasCycle()` Does the digraph have a directed cycle?
`static void`	`main(String[] args)` Unit tests the `DirectedCycle` data type.

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DirectedCycle
```
public DirectedCycle(Digraph G)
```
    Determines whether the digraph G has a directed cycle and, if so, finds such a cycle.
    
    Parameters:
    
    G - the digraph
- Method Detail
  - hasCycle
```
public boolean hasCycle()
```
    Does the digraph have a directed cycle?
    
    Returns:
    
    true if the digraph has a directed cycle, false otherwise
  - cycle
```
public Iterable<Integer> cycle()
```
    Returns a directed cycle if the digraph has a directed cycle, and null otherwise.
    
    Returns:
    
    a directed cycle (as an iterable) if the digraph has a directed cycle, and null otherwise
  - main
```
public static void main(String[] args)
```
    Unit tests the DirectedCycle data type.
    
    Parameters:
    
    args - the command-line arguments