Class Combinations
java.lang.Object
org.apache.commons.numbers.combinatorics.Combinations
- All Implemented Interfaces:
Iterable<int[]>
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
Defines a lexicographic ordering of the combinations.private static class
Lexicographic combinations iterator.private static class
Iterator with just one element to handle degenerate cases (full array, empty array) for combination iterator. -
Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionComparator
<int[]> Creates a comparator.int
getK()
Gets the number of elements in each combination.int
getN()
Gets the size of the set from which combinations are drawn.Iterator
<int[]> iterator()
Creates an iterator whose range is the k-element subsets of {0, ..., n - 1} represented asint[]
arrays.static Combinations
of
(int n, int k) Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Field Details
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n
private final int nSize of the set from which combinations are drawn. -
k
private final int kNumber of elements in each combination.
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Constructor Details
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Combinations
private Combinations(int n, int k) - Parameters:
n
- Size of the set from which subsets are selected.k
- Size of the subsets to be enumerated.- Throws:
IllegalArgumentException
- ifn < 0
.IllegalArgumentException
- ifk > n
ork < 0
.
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Method Details
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of
- Parameters:
n
- Size of the set from which subsets are selected.k
- Size of the subsets to be enumerated.- Returns:
- a new instance.
- Throws:
IllegalArgumentException
- ifn < 0
.IllegalArgumentException
- ifk > n
ork < 0
.
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getN
public int getN()Gets the size of the set from which combinations are drawn.- Returns:
- the size of the universe.
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getK
public int getK()Gets the number of elements in each combination.- Returns:
- the size of the subsets to be enumerated.
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iterator
Creates an iterator whose range is the k-element subsets of {0, ..., n - 1} represented asint[]
arrays.The iteration order is lexicographic: the arrays returned by the
Ifiterator
are sorted in descending order and they are visited in lexicographic order with significance from right to left. For example,new Combinations(4, 2).iterator()
returns an iterator that will generate the following sequence of arrays on successive calls tonext()
:
[0, 1], [0, 2], [1, 2], [0, 3], [1, 3], [2, 3]
k == 0
an iterator containing an empty array is returned; ifk == n
an iterator containing [0, ..., n - 1] is returned. -
comparator
Creates a comparator. When performing a comparison, if an element of the array is not within the interval [0,n
), anIllegalArgumentException
will be thrown.- Returns:
- a comparator.
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