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[Java] Class PermutationGenerator<E>

groovy.util.PermutationGenerator

All Implemented Interfaces and Traits:: Iterator

public class PermutationGenerator<E>
extends Object
implements Iterator

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

Methods Summary

Methods
Type Params	Return Type	Name and description
	`public BigInteger`	`getTotal()`
	`public boolean`	`hasNext()`
	`public List<E>`	`next()` Generate next permutation (algorithm from Rosen p. 284)
	`public void`	`remove()`
	`public void`	`reset()`

Inherited Methods Summary

Inherited Methods
Methods inherited from class	Name
`class Object`	`wait, wait, wait, equals, toString, hashCode, getClass, notify, notifyAll`

Constructor Detail

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

public PermutationGenerator(Iterable<E> items)

Method Detail

public BigInteger getTotal()

public boolean hasNext()

public List<E> next()

Generate next permutation (algorithm from Rosen p. 284)

Returns:: the items permuted

public void remove()

public void reset()

© 2003-2020 The Apache Software Foundation
Licensed under the Apache license.
https://docs.groovy-lang.org/3.0.7/html/gapi/groovy/util/PermutationGenerator.html