com.datumbox.framework.core.mathematics.discrete

Class Combinatorics

java.lang.Object

com.datumbox.framework.core.mathematics.discrete.Combinatorics

public class Combinatorics
extends java.lang.Object

Utility class for combinations and permutations.

Constructor Summary

Constructors

Constructor and Description
Combinatorics()

Method Summary

Modifier and Type	Method and Description
static <T> java.util.Set<java.util.Set<T>>	combinations(java.util.Set<T> elements, int subsetSize) Returns all the possible combinations of the set.
static <T> java.util.Iterator<T[]>	combinationsIterator(T[] elements, int subsetSize) Fast and memory efficient way to return an iterator with all the possible combinations of an array.
static <T> java.util.stream.Stream<java.util.Set<T>>	combinationsStream(java.util.Set<T> elements, int subsetSize) Returns all the possible combinations of the set in a stream.
static <T> java.util.Collection<java.util.List<T>>	permutations(java.util.Collection<T> elements) Returns the permutations of a collection.

Methods inherited from class java.lang.Object

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

Constructor Detail

Combinatorics

public Combinatorics()

Method Detail

permutations

public static <T> java.util.Collection<java.util.List<T>> permutations(java.util.Collection<T> elements)

Returns the permutations of a collection. Ported from: http://stackoverflow.com/questions/10503392/java-code-for-permutations-of-a-list-of-numbers

Type Parameters:

T -

Parameters:

elements -

Returns:

combinations

public static <T> java.util.Set<java.util.Set<T>> combinations(java.util.Set<T> elements,
                                                               int subsetSize)

Returns all the possible combinations of the set.

Type Parameters:

T -

Parameters:

elements -

subsetSize -

Returns:

combinationsStream

public static <T> java.util.stream.Stream<java.util.Set<T>> combinationsStream(java.util.Set<T> elements,
                                                                               int subsetSize)

Returns all the possible combinations of the set in a stream. Heavily Modified code: http://codereview.stackexchange.com/questions/26854/recursive-method-to-return-a-set-of-all-combinations

Type Parameters:

T -

Parameters:

elements -

subsetSize -

Returns:

combinationsIterator

public static <T> java.util.Iterator<T[]> combinationsIterator(T[] elements,
                                                               int subsetSize)

Fast and memory efficient way to return an iterator with all the possible combinations of an array. Heavily Modified code: http://hmkcode.com/calculate-find-all-possible-combinations-of-an-array-using-java/

Type Parameters:

T -

Parameters:

elements -

subsetSize -

Returns: