de.ipcon.tools

Class PermutationGenerator

java.lang.Object

de.ipcon.tools.PermutationGenerator

public class PermutationGenerator
extends java.lang.Object

Systematically generate all permutations of a given integer range. Based on source code from http://www.merriampark.com/perm.htm which "is free for you to use in whatever way you wish."

Constructor Summary

Constructors

Constructor and Description
PermutationGenerator(int _n) Constructor.

Method Summary

Modifier and Type	Method and Description
int[]	getCurrent()
int[]	getNext() Generate next permutation (algorithm from Rosen p. 284).
java.math.BigInteger	getNumLeft() Return number of permutations not yet generated.
java.math.BigInteger	getTotal() Return total number of permutations.
boolean	hasMore() Are there more permutations?
void	reset() Reset the generator.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PermutationGenerator

public PermutationGenerator(int _n)

Constructor. 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.

Method Detail

reset

public void reset()

Reset the generator.

getNumLeft

public java.math.BigInteger getNumLeft()

Return number of permutations not yet generated.

getTotal

public java.math.BigInteger getTotal()

Return total number of permutations.

hasMore

public boolean hasMore()

Are there more permutations?

getNext

public int[] getNext()

Generate next permutation (algorithm from Rosen p. 284).

getCurrent

public int[] getCurrent()