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Message:

How do I change the sort order in this code?

Posted by Sandra on August 08, 2000 at 7:20 AM

/*
* MergeSort.java
*
* Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved.
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information"). You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*
*/

/**
* An implementation of MergeSort, needs to be subclassed to
* compare the terms.
*
* @author Scott Violet
*/
public abstract class MergeSort extends Object {
protected Object toSort[];
protected Object swapSpace[];

public void sort(Object array[]) {
if(array != null && array.length > 1)
{
int maxLength;

maxLength = array.length;
swapSpace = new Object[maxLength];
toSort = array;
this.mergeSort(0, maxLength - 1);
swapSpace = null;
toSort = null;
}
}

public abstract int compareElementsAt(int beginLoc, int endLoc);

protected void mergeSort(int begin, int end) {
if(begin != end)
{
int mid;

mid = (begin + end) / 2;
this.mergeSort(begin, mid);
this.mergeSort(mid + 1, end);
this.merge(begin, mid, end);
}
}

protected void merge(int begin, int middle, int end) {
int firstHalf, secondHalf, count;

firstHalf = count = begin;
secondHalf = middle + 1;
while((firstHalf <= middle) && (secondHalf <= end))
{
if(this.compareElementsAt(secondHalf, firstHalf) < 0)
swapSpace[count++] = toSort[secondHalf++];
else
swapSpace[count++] = toSort[firstHalf++];
}
if(firstHalf <= middle)
{
while(firstHalf <= middle)
swapSpace[count++] = toSort[firstHalf++];
}
else
{
while(secondHalf <= end)
swapSpace[count++] = toSort[secondHalf++];
}
for(count = begin;count <= end;count++)
toSort[count] = swapSpace[count];
}
}