cc.redberry.core.combinatorics

Class IntCombinationsGenerator

java.lang.Object

cc.redberry.core.combinatorics.IntCombinatorialGenerator

cc.redberry.core.combinatorics.IntCombinationsGenerator

All Implemented Interfaces:

IntCombinatorialPort, OutputPort<int[]>, java.lang.Iterable<int[]>, java.util.Iterator<int[]>

public final class IntCombinationsGenerator
extends IntCombinatorialGenerator
implements IntCombinatorialPort

This class represents an iterator over all unordered combinations (i.e. [0,1] and [1,0] are considered as same, so only [0,1] will appear in the sequence) of k numbers, which can be chosen from the set of n numbers (0,1,2,...,n). The total number of such combinations is a binomial coefficient n!/(k!(n-k)!). Each returned array is sorted.

The iterator is implemented such that each next combination will be calculated only on the invocation of method next().

Note: method next() returns the same reference on each invocation. So, if it is needed not only to obtain the information from next(), but also save the result, it is necessary to clone the returned array.

Since:

1.0

Nested Class Summary

Nested classes/interfaces inherited from interface cc.redberry.core.utils.OutputPort

OutputPort.PortIterable<T>, OutputPort.PortIterator<T>, OutputPort.Singleton<T>

Constructor Summary

Constructors

Constructor and Description
IntCombinationsGenerator(int n, int k)

Method Summary

Modifier and Type	Method and Description
int[]	getReference() Returns the reference on the current iteration element.
boolean	hasNext()
int[]	next()
void	remove()
void	reset() Resets the iteration
int[]	take() Calculates and returns the next combination or null, if no more combinations exist.

Methods inherited from class cc.redberry.core.combinatorics.IntCombinatorialGenerator

iterator

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

IntCombinationsGenerator

public IntCombinationsGenerator(int n,
                                int k)

Method Detail

take

public int[] take()

Description copied from interface: IntCombinatorialPort

Calculates and returns the next combination or null, if no more combinations exist.

Specified by:

take in interface IntCombinatorialPort

Specified by:

take in interface OutputPort<int[]>

Returns:

the next combination or null, if no more combinations exist

hasNext

public boolean hasNext()

Specified by:

hasNext in interface java.util.Iterator<int[]>

reset

public void reset()

Description copied from class: IntCombinatorialGenerator

Resets the iteration

Specified by:

reset in interface IntCombinatorialPort

Specified by:

reset in class IntCombinatorialGenerator

next

public int[] next()

Specified by:

next in interface java.util.Iterator<int[]>

remove

public void remove()

Specified by:

remove in interface java.util.Iterator<int[]>

Throws:

java.lang.UnsupportedOperationException - always

getReference

public int[] getReference()

Description copied from class: IntCombinatorialGenerator

Returns the reference on the current iteration element.

Specified by:

getReference in interface IntCombinatorialPort

Specified by:

getReference in class IntCombinatorialGenerator

Returns:

the reference on the current iteration element