edu.princeton.cs.algs4

## Class Cycle

• Object
• edu.princeton.cs.algs4.Cycle

• ```public class Cycle
extends Object```
The `Cycle` class represents a data type for determining whether an undirected graph has a simple cycle. The hasCycle operation determines whether the graph has a 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. (The depth-first search part takes only O(V) time; however, checking for self-loops and parallel edges takes Θ(V + E) time in the worst case.) Each instance method takes Θ(1) time. It uses Θ(V) extra space (not including the graph).

For additional documentation, see Section 4.1 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:
Robert Sedgewick, Kevin Wayne
• ### Constructor Summary

Constructors
Constructor and Description
`Cycle(Graph G)`
Determines whether the undirected graph `G` has a cycle and, if so, finds such a cycle.
• ### Method Summary

All Methods
Modifier and Type Method and Description
`Iterable<Integer>` `cycle()`
Returns a cycle in the graph `G`.
`boolean` `hasCycle()`
Returns true if the graph `G` has a cycle.
`static void` `main(String[] args)`
Unit tests the `Cycle` data type.
• ### Methods inherited from class Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Constructor Detail

• #### Cycle

`public Cycle(Graph G)`
Determines whether the undirected graph `G` has a cycle and, if so, finds such a cycle.
Parameters:
`G` - the undirected graph
• ### Method Detail

• #### hasCycle

`public boolean hasCycle()`
Returns true if the graph `G` has a cycle.
Returns:
`true` if the graph has a cycle; `false` otherwise
• #### cycle

`public Iterable<Integer> cycle()`
Returns a cycle in the graph `G`.
Returns:
a cycle if the graph `G` has a cycle, and `null` otherwise
• #### main

`public static void main(String[] args)`
Unit tests the `Cycle` data type.
Parameters:
`args` - the command-line arguments