de.jstacs.models.discrete.inhomogeneous
Class CombinationIterator

java.lang.Object
  de.jstacs.models.discrete.inhomogeneous.CombinationIterator

public class CombinationIterator
extends Object

This class can be used for iterating over all possible combinations (in the sense of combinatorics).

Author:

Jens Keilwagen

Constructor Summary

CombinationIterator(int n, int max)
Creates a new CombinationIterator with n elements and at most max selected elements.

Method Summary

int[]	getCombination() Returns a clone of the internal combination.
long	getIndex(int[] combi) This method returns an index for the sorted entries of a combination combi.
long	getNumberOfCombinations(int elements) Returns the number of possible combinations.
boolean	next() Steps to the next combination.
void	reset() This method resets the internal combination.
void	setCurrentLength(int current) This method sets the current used number of selected elements.

Methods inherited from class java.lang.Object

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

Constructor Detail

CombinationIterator

public CombinationIterator(int n,
                           int max)

Creates a new CombinationIterator with n elements and at most max selected elements.

Parameters:

n - the number of elements

max - the maximal number of selected elements

Method Detail

getNumberOfCombinations

public long getNumberOfCombinations(int elements)
                             throws IllegalArgumentException

Returns the number of possible combinations.

Parameters:

elements - the number of selected elements

Returns:

the number of possible combinations

Throws:

IllegalArgumentException - if elements < 0

setCurrentLength

public void setCurrentLength(int current)
                      throws IllegalArgumentException

This method sets the current used number of selected elements.

Parameters:

current - the current used number of selected elements

Throws:

IllegalArgumentException - if current < 0 or current > max

See Also:

reset()

next

public boolean next()
             throws IllegalArgumentException

Steps to the next combination.

Returns:

true if the method does not run out of range, false otherwise

Throws:

IllegalArgumentException - if the method setCurrentLength(int)was not used to set the current used number of selected elements

getCombination

public int[] getCombination()

Returns a clone of the internal combination.

Returns:

a clone of the internal combination

getIndex

public long getIndex(int[] combi)

This method returns an index for the sorted entries of a combination combi.

Parameters:

combi - the combination

Returns:

the index

reset

public void reset()
           throws IllegalArgumentException

This method resets the internal combination.

Throws:

IllegalArgumentException - if the method setCurrentLength(int) was not used to set the current used number of selected elements