com.phloc.commons.math

Class CombinationGenerator<DATATYPE>

java.lang.Object

com.phloc.commons.math.CombinationGenerator<DATATYPE>

Type Parameters:

DATATYPE - element type

All Implemented Interfaces:

IIterableIterator<List<DATATYPE>>, Iterable<List<DATATYPE>>, Iterator<List<DATATYPE>>

public final class CombinationGenerator<DATATYPE>
extends Object
implements IIterableIterator<List<DATATYPE>>

Utility class for generating all possible combinations of elements for a specified number of available slots. Duplicates in the passed elements will be treated as different individuals and hence deliver duplicate result solutions. This generator will only return complete result sets filling all slots.

Author:

Boris Gregorcic, Philip Helger

Constructor Summary

Constructors

Constructor and Description
CombinationGenerator(List<DATATYPE> aElements, int nSlotCount) Ctor

Method Summary

Methods

Modifier and Type	Method and Description
static <DATATYPE> void	addAllPermutations(List<DATATYPE> aInput, int nSlotCount, Collection<List<DATATYPE>> aResultList) Fill a list with all permutations of the input elements.
static <DATATYPE> List<List<DATATYPE>>	getAllPermutations(List<DATATYPE> aInput, int nSlotCount) Get a list of all permutations of the input elements.
BigInteger	getCombinationsLeft()
BigInteger	getTotalCombinations()
boolean	hasNext()
Iterator<List<DATATYPE>>	iterator()
List<DATATYPE>	next() Generate next combination (algorithm from Rosen p. 286)
void	remove()
void	reset() Reset the generator

Methods inherited from class java.lang.Object

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

Constructor Detail

CombinationGenerator

public CombinationGenerator(@Nonnull@Nonempty
                    List<DATATYPE> aElements,
                    @Nonnegative
                    int nSlotCount)

Ctor

Parameters:

aElements - the elements to fill into the slots for creating all combinations (must not be empty!)

nSlotCount - the number of slots to use (must not be greater than the element count!)

Method Detail

reset

public void reset()

Reset the generator

getCombinationsLeft

@Nonnull
public BigInteger getCombinationsLeft()

Returns:

number of combinations not yet generated

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<List<DATATYPE>>

Returns:

whether or not there are more combinations left

getTotalCombinations

@Nonnull
public BigInteger getTotalCombinations()

Returns:

total number of combinations

next

@Nonnull
@ReturnsMutableCopy
public List<DATATYPE> next()

Generate next combination (algorithm from Rosen p. 286)

Specified by:

next in interface IIterableIterator<List<DATATYPE>>

Specified by:

next in interface Iterator<List<DATATYPE>>

Returns:

the next combination as List of the size specified for slots filled with elements from the original list

remove

@UnsupportedOperation
public void remove()

Specified by:

remove in interface Iterator<List<DATATYPE>>

iterator

@Nonnull
public Iterator<List<DATATYPE>> iterator()

Specified by:

iterator in interface Iterable<List<DATATYPE>>

getAllPermutations

@Nonnull
public static <DATATYPE> List<List<DATATYPE>> getAllPermutations(@Nonnull@Nonempty
                                                         List<DATATYPE> aInput,
                                                         @Nonnegative
                                                         int nSlotCount)

Get a list of all permutations of the input elements.

Parameters:

aInput - Input list.

nSlotCount - Slot count.

Returns:

The list of all permutations. Beware: the resulting list may be quite large and may contain duplicates if the input list contains duplicate elements!

addAllPermutations

public static <DATATYPE> void addAllPermutations(@Nonnull@Nonempty
                                 List<DATATYPE> aInput,
                                 @Nonnegative
                                 int nSlotCount,
                                 @Nonnull
                                 Collection<List<DATATYPE>> aResultList)

Fill a list with all permutations of the input elements.

Parameters:

aInput - Input list.

nSlotCount - Slot count.

aResultList - The list to be filled with all permutations. Beware: this list may be quite large and may contain duplicates if the input list contains duplicate elements! Note: this list is not cleared before filling