jhplot.math

Class SortUtils

java.lang.Object

jhplot.math.SortUtils

public class SortUtils
extends Object

Utility class providing some useful static sort methods. The sort routines all return index permutations p such that data[p[0]],..,data[p[data.length-1]] is in sorted order. The data array itself is not modified. To actually rearrange the array elements, the inverse of p can be used to permute the array, such that data[0],..,data[data.length-1] is in sorted order. Use getIterator(p, data) to iterate in sorted order. A code example may show you what to do next:

 String[] colors = { "red", "green", "blue" };
 int[] p = SortUtils.sort(colors, new StringComparator());
 // --> (colors[p[0]], colors[p[1]], colors[p[2]]) == ("blue","green","red")
 Iterator iter = SortUtils.getIterator(p, colors)
 // --> (iter.next(), iter.next(), iter.next()) == ("blue","green","red")
 SortUtils.permute(SortUtils.inverse(p), colors, true);
 // --> (colors[0], colors[1], colors[2]) == ("blue","green","red")
 

Stable sorts (preserving order of equal elements) are supported. Sorting is done using quick-sort mith median of 3 (and insertion-sort for small ranges).

Constructor Summary

Constructors

Constructor and Description
SortUtils()

Method Summary

Modifier and Type	Method and Description
static Iterator	getIterator(int[] p, List data) Answer iterator, which iterates over specified data list according to the specified permutation, that is data.get(p[0]),..,data.get(p[data.length-1])
static Iterator	getIterator(int[] p, Object[] data) Answer iterator, which iterates over specified data array according to the specified permutation, that is data[p[0]],..,data[p[data.length-1]]
static int[]	identity(int n) Create identity permutation, that is {0, 1, ..., n}
static int[]	inverse(int[] p) Compute inverse permutation
static void	main(String[] args) Test method
static Object[]	permute(int[] p, Object[] data, boolean clone) Rearrange the specified data according to the specified permutation.
static int[]	reverse(int n) Create reverse permutation, that is {n-1, ....
static void	sort(int[] indices, Object[] data, Comparator comparator) Do an unstable sort.
static void	sort(int[] indices, Object[] data, Comparator comparator, boolean stable) Do a sort on indices.
static int[]	sort(Object[] data, Comparator comparator) Do an unstable sort.
static int[]	sort(Object[] data, Comparator comparator, boolean stable) Do a sort on indices.

Methods inherited from class java.lang.Object

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

Constructor Detail

SortUtils

public SortUtils()

Method Detail

identity

public static int[] identity(int n)

Create identity permutation, that is {0, 1, ..., n}

reverse

public static int[] reverse(int n)

Create reverse permutation, that is {n-1, .... 1, 0}

inverse

public static int[] inverse(int[] p)

Compute inverse permutation

permute

public static Object[] permute(int[] p,
                               Object[] data,
                               boolean clone)

Rearrange the specified data according to the specified permutation. That is, the array is rearranged, such that data_after[p[i]] == data_before[i].

Parameters:

data - data to be permuted

p - the permutation

clone - if true, rearrange a clone instead of the original data;

Returns:

the permuted array (which is the original reference if clone == false)

getIterator

public static Iterator getIterator(int[] p,
                                   Object[] data)

Answer iterator, which iterates over specified data array according to the specified permutation, that is data[p[0]],..,data[p[data.length-1]]

getIterator

public static Iterator getIterator(int[] p,
                                   List data)

Answer iterator, which iterates over specified data list according to the specified permutation, that is data.get(p[0]),..,data.get(p[data.length-1])

sort

public static void sort(int[] indices,
                        Object[] data,
                        Comparator comparator,
                        boolean stable)

Do a sort on indices.

Parameters:

data - data to be sorted

comparator - comparator to use

stable - do a stable sort iff true

indices - into data (any permutation of 0,..data.length-1).

sort

public static int[] sort(Object[] data,
                         Comparator comparator,
                         boolean stable)

Do a sort on indices.

Parameters:

data - data to be sorted

comparator - comparator to use

stable - do a stable sort iff true

Returns:

permutation p such that data[p[0]],..,data[p[data.length-1]] is in sorted order

sort

public static int[] sort(Object[] data,
                         Comparator comparator)

Do an unstable sort.

Parameters:

data - data to be sorted

comparator - comparator to use

Returns:

permutation p such that data[p[0]],..,data[p[data.length-1]] is in sorted order

sort

public static void sort(int[] indices,
                        Object[] data,
                        Comparator comparator)

Do an unstable sort.

Parameters:

data - data to be sorted

indices - into data (permutation of 0,..data.length-1).

main

public static void main(String[] args)

Test method