gov.sandia.cognition.math

Class Permutation

java.lang.Object

gov.sandia.cognition.math.Permutation

@CodeReview(reviewer="Kevin R. Dixon",
            date="2008-02-26",
            changesNeeded=false,
            comments="Looks good.")
public class Permutation
extends java.lang.Object

The Permutation class contains methods for dealing with permutations of object sets.

Since:

1.0

Author:

Justin Basilico

Constructor Summary

Constructors

Constructor and Description
Permutation() Creates a new instance of Permutation

Method Summary

Modifier and Type	Method and Description
static int[]	createPartialPermutation(int n, int k, java.util.Random random) Creates a random partial permutation of size k of the numbers 0 (inclusive) through n (exclusive).
static int[]	createPermutation(int n, java.util.Random random) Creates a random permutation of the numbers 0 (inclusive) through n (exclusive).
static <DataType> java.util.ArrayList<DataType>	createReordering(java.util.Collection<? extends DataType> collection, java.util.Random random) Takes a collection and returns an array list that contains a permutation of the elements of that collection.
static <DataType> void	reorder(java.util.ArrayList<DataType> list, java.util.Random random) Reorders the elements in a given array list to be a permuted ordering of elements in the collection.

Methods inherited from class java.lang.Object

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

Constructor Detail

Permutation

public Permutation()

Creates a new instance of Permutation

Method Detail

reorder

public static <DataType> void reorder(java.util.ArrayList<DataType> list,
                                      java.util.Random random)

Reorders the elements in a given array list to be a permuted ordering of elements in the collection.

Type Parameters:

DataType - The data type of the list to reorder.

Parameters:

list - The array list to reorder.

random - The random number generator to use.

createReordering

public static <DataType> java.util.ArrayList<DataType> createReordering(java.util.Collection<? extends DataType> collection,
                                                                        java.util.Random random)

Takes a collection and returns an array list that contains a permutation of the elements of that collection.

Type Parameters:

DataType - Data class to reorder

Parameters:

collection - The collection to create a permutation of.

random - The random number generator to use.

Returns:

A permutation of the given collection.

createPermutation

public static int[] createPermutation(int n,
                                      java.util.Random random)

Creates a random permutation of the numbers 0 (inclusive) through n (exclusive). The permutation contains the all the numbers 0 through n in a random order. There are no duplicates.

Parameters:

n - The size of the permutation.

random - The Random generator to use.

Returns:

A random permutation of the numbers 0 through n.

createPartialPermutation

public static int[] createPartialPermutation(int n,
                                             int k,
                                             java.util.Random random)

Creates a random partial permutation of size k of the numbers 0 (inclusive) through n (exclusive). The permutation contains k unique values of the numbers 0 through n in a random order. There are no duplicates.

Parameters:

n - The size of the set of numbers to get values of the partial permutation from.

k - The size of the partial permutation. Must be less than or equal to n. Cannot be negative.

random - The Random generator to use.

Returns:

A random permutation of the numbers 0 through n.