Package com.helger.commons.math

Class CombinationGenerator<DATATYPE>

java.lang.Object

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

Type Parameters:

DATATYPE - Element type to be combined

All Implemented Interfaces:

ICommonsIterable<ICommonsList<DATATYPE>>, IIterableIterator<ICommonsList<DATATYPE>>, Iterable<ICommonsList<DATATYPE>>, Iterator<ICommonsList<DATATYPE>>

public class CombinationGenerator<DATATYPE>
extends Object
implements IIterableIterator<ICommonsList<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	Description
CombinationGenerator(ICommonsList<DATATYPE> aElements, int nSlotCount)	Ctor

Method Summary

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.helger.commons.collection.impl.ICommonsIterable

containsAny, containsNone, containsOnly, findAll, findAllInstanceOf, findAllMapped, findAllMapped, findAllMapped, findFirst, findFirst, findFirstIndex, findFirstMapped, findFirstMapped, findLastIndex, forEachBreakable, forEachByIndex, forEachThrowing, getCount, getCount

Methods inherited from interface com.helger.commons.collection.iterate.IIterableIterator

iterator, withFilter, withMapper

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Constructor Detail

CombinationGenerator

public CombinationGenerator(@Nonnull @Nonempty
                            ICommonsList<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 final 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<DATATYPE>

Returns:

whether or not there are more combinations left

getTotalCombinations

@Nonnull
public BigInteger getTotalCombinations()

Returns:

total number of combinations

next

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

Generate next combination (algorithm from Rosen p. 286)

Specified by:

next in interface Iterator<DATATYPE>

Returns:

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

getAllPermutations

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

Get a list of all permutations of the input elements.

Type Parameters:

DATATYPE - Element type to be combined

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
                                                 ICommonsList<DATATYPE> aInput,
                                                 @Nonnegative
                                                 int nSlotCount,
                                                 @Nonnull
                                                 Collection<ICommonsList<DATATYPE>> aResultList)

Fill a list with all permutations of the input elements.

Type Parameters:

DATATYPE - Element type to be combined

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