Groovy 2.2.1

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()


next

public List next()
Generate next permutation (algorithm from Rosen p. 284)
Returns:
the items permuted


remove

public void remove()


reset

public void reset()


 

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