Package com.espertech.esper.common.internal.collection

Class PermutationEnumeration

java.lang.Object

com.espertech.esper.common.internal.collection.PermutationEnumeration

All Implemented Interfaces:

Enumeration<int[]>

public class PermutationEnumeration
extends Object
implements Enumeration<int[]>

Provides a N! (n-faculty) number of permutations for N elements. Example: for 3 elements provides 6 permutations exactly as follows: {0, 1, 2} {0, 2, 1} {1, 0, 2} {1, 2, 0} {2, 0, 1} {2, 1, 0}

Constructor Summary

Constructors

Constructor	Description
PermutationEnumeration(int numElements)	Ctor.

Method Summary

Modifier and Type	Method	Description
protected static int	faculty(int num)	Computes faculty of N.
protected static int[]	getFactors(int numElements)	Returns factors for computing the permutation.
protected static int[]	getPermutation(int numElements, int permutation, int[] factors)	Returns permutation.
boolean	hasMoreElements()
int[]	nextElement()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Enumeration

asIterator

Constructor Details

PermutationEnumeration

public PermutationEnumeration(int numElements)

Ctor.

Parameters:

numElements - - number of elements in each permutation.

Method Details

hasMoreElements

public boolean hasMoreElements()

Specified by:

hasMoreElements in interface Enumeration<int[]>

nextElement

public int[] nextElement()

Specified by:

nextElement in interface Enumeration<int[]>

getPermutation

protected static int[] getPermutation(int numElements,
 int permutation,
 int[] factors)

Returns permutation.

Parameters:

numElements - - number of elements in each permutation

permutation - - number of permutation to compute, between 0 and numElements!

factors - - factors for each index

Returns:

permutation

getFactors

protected static int[] getFactors(int numElements)

Returns factors for computing the permutation.

Parameters:

numElements - - number of factors to compute

Returns:

factors list

faculty

protected static int faculty(int num)

Computes faculty of N.

Parameters:

num - to compute faculty for

Returns:

N!