PermutationGenerator (Groovy 2.5.18)

java.lang.Object
- groovy.util.PermutationGenerator<E>

All Implemented Interfaces:

Iterator<List<E>>
```
public class PermutationGenerator<E>
extends Object
implements Iterator<List<E>>
```
Systematically generate permutations. Adapted from Java Code by Michael Gilleland (released with no restrictions) using an algorithm described here: Kenneth H. Rosen, Discrete Mathematics and Its Applications, 2nd edition (NY: McGraw-Hill, 1991), pp. 282-284

Constructor Summary

Constructors
Constructor Description

PermutationGenerator(Iterable<E> items)

PermutationGenerator(Collection<E> items)
WARNING: Don't make n too large.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`BigInteger`	`getTotal()`
`boolean`	`hasNext()`
`List<E>`	`next()`	Generate next permutation (algorithm from Rosen p.
`void`	`remove()`
`void`	`reset()`

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

Methods inherited from interface java.util.Iterator
forEachRemaining

- Constructor Detail
  - PermutationGenerator
```
public PermutationGenerator(Collection<E> items)
```
    WARNING: Don't make n too large. Recall that the number of permutations is n! which can be very large, even when n is as small as 20 -- 20! = 2,432,902,008,176,640,000 and 21! is too big to fit into a Java long, which is why we use BigInteger instead.
    
    Parameters:
    
    items - the items to permute
  - PermutationGenerator
```
public PermutationGenerator(Iterable<E> items)
```
- Method Detail
  - reset
```
public void reset()
```
  - getTotal
```
public BigInteger getTotal()
```
  - hasNext
```
public boolean hasNext()
```
    Specified by:
    
    hasNext in interface Iterator<E>
  - next
```
public List<E> next()
```
    Generate next permutation (algorithm from Rosen p. 284)
    
    Specified by:
    
    next in interface Iterator<E>
    
    Returns:
    
    the items permuted
  - remove
```
public void remove()
```
    Specified by:
    
    remove in interface Iterator<E>