PermutationGenerator (groovy 2.2.0 API)

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Groovy 2.2.0

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groovy.util
[Java] Class PermutationGenerator

java.lang.Object
  groovy.util.PermutationGenerator

All Implemented Interfaces:: Iterator

public class PermutationGenerator
extends Object

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
`PermutationGenerator(Collection items)` WARNING: Don't make n too large.

Method Summary
`BigInteger`	`getTotal()`
`boolean`	`hasNext()`
`List`	`next()` Generate next permutation (algorithm from Rosen p. 284)
`void`	`remove()`
`void`	`reset()`

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

Constructor Detail

PermutationGenerator

public PermutationGenerator(Collection 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

Method Detail

getTotal

public BigInteger getTotal()

hasNext

public boolean hasNext()

public List next()

Generate next permutation (algorithm from Rosen p. 284)

Returns:: the items permuted

remove

public void remove()

reset

public void reset()

groovy.util [Java] Class PermutationGenerator