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Added shuffle() variants that allow passing in the random object from

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which random values are obtained.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@953 6335cc39-0255-0410-8fd6-9bcaacd3b74c
This commit is contained in:
shaper
2002-11-29 20:39:21 +00:00
parent 44fc9cf753
commit 9c8652d369
1 changed files with 92 additions and 8 deletions
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projects/samskivert/src/java/com/samskivert/util/ArrayUtil.java
+92 -8
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@@ -1,5 +1,5 @@
//
// $Id: ArrayUtil.java,v 1.18 2002/11/08 02:34:54 shaper Exp $
// $Id: ArrayUtil.java,v 1.19 2002/11/29 20:39:21 shaper Exp $
//
// samskivert library - useful routines for java programs
// Copyright (C) 2001 Walter Korman
@@ -172,7 +172,19 @@ public class ArrayUtil
*/
public static void shuffle (byte[] values)
{
shuffle(values, 0, values.length);
shuffle(values, _rnd);
}
/**
* Shuffles the elements in the given array into a random sequence.
*
* @param values the array to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (byte[] values, Random rnd)
{
shuffle(values, 0, values.length, rnd);
}
/**
@@ -184,12 +196,28 @@ public class ArrayUtil
* @param length the number of elements to shuffle.
*/
public static void shuffle (byte[] values, int offset, int length)
{
shuffle(values, offset, length, _rnd);
}
/**
* Shuffles a subset of elements within the specified array into a
* random sequence.
*
* @param values the array containing elements to shuffle.
* @param offset the index at which to start shuffling elements.
* @param length the number of elements to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (
byte[] values, int offset, int length, Random rnd)
{
// starting from the end of the specified region, repeatedly swap
// the element in question with a random element previous to it
// (in the specified region) up to and including itself
for (int ii = offset + length - 1; ii > offset; ii--) {
int idx = offset + _rnd.nextInt(ii - offset + 1);
int idx = offset + rnd.nextInt(ii - offset + 1);
byte tmp = values[ii];
values[ii] = values[idx];
values[idx] = tmp;
@@ -203,7 +231,19 @@ public class ArrayUtil
*/
public static void shuffle (int[] values)
{
shuffle(values, 0, values.length);
shuffle(values, _rnd);
}
/**
* Shuffles the elements in the given array into a random sequence.
*
* @param values the array to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (int[] values, Random rnd)
{
shuffle(values, 0, values.length, rnd);
}
/**
@@ -215,12 +255,28 @@ public class ArrayUtil
* @param length the number of elements to shuffle.
*/
public static void shuffle (int[] values, int offset, int length)
{
shuffle(values, offset, length, _rnd);
}
/**
* Shuffles a subset of elements within the specified array into a
* random sequence.
*
* @param values the array containing elements to shuffle.
* @param offset the index at which to start shuffling elements.
* @param length the number of elements to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (
int[] values, int offset, int length, Random rnd)
{
// starting from the end of the specified region, repeatedly swap
// the element in question with a random element previous to it
// (in the specified region) up to and including itself
for (int ii = offset + length - 1; ii > offset; ii--) {
int idx = offset + _rnd.nextInt(ii - offset + 1);
int idx = offset + rnd.nextInt(ii - offset + 1);
int tmp = values[ii];
values[ii] = values[idx];
values[idx] = tmp;
@@ -234,7 +290,19 @@ public class ArrayUtil
*/
public static void shuffle (Object[] values)
{
shuffle(values, 0, values.length);
shuffle(values, _rnd);
}
/**
* Shuffles the elements in the given array into a random sequence.
*
* @param values the array to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (Object[] values, Random rnd)
{
shuffle(values, 0, values.length, rnd);
}
/**
@@ -246,12 +314,28 @@ public class ArrayUtil
* @param length the number of elements to shuffle.
*/
public static void shuffle (Object[] values, int offset, int length)
{
shuffle(values, offset, length, _rnd);
}
/**
* Shuffles a subset of elements within the specified array into a
* random sequence.
*
* @param values the array containing elements to shuffle.
* @param offset the index at which to start shuffling elements.
* @param length the number of elements to shuffle.
* @param rnd the source from which random values for shuffling the
* array are obtained.
*/
public static void shuffle (
Object[] values, int offset, int length, Random rnd)
{
// starting from the end of the specified region, repeatedly swap
// the element in question with a random element previous to it
// (in the specified region) up to and including itself
for (int ii = offset + length - 1; ii > offset; ii--) {
int idx = offset + _rnd.nextInt(ii - offset + 1);
int idx = offset + rnd.nextInt(ii - offset + 1);
Object tmp = values[ii];
values[ii] = values[idx];
values[idx] = tmp;
@@ -595,6 +679,6 @@ public class ArrayUtil
return nvalues;
}
/** The random object used when shuffling an array. */
/** The default random object used when shuffling an array. */
protected static Random _rnd = new Random();
}