[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
| Constructor and description |
|---|
PermutationGenerator
(Collection<E> items)WARNING: Don't make n too large. |
PermutationGenerator
(Iterable<E> items) |
Methods Summary
| 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
| 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