org.jgrasstools.gears.utils.sorting.QuickSortAlgorithmObjects Maven / Gradle / Ivy
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/*
* JGrass - Free Open Source Java GIS http://www.jgrass.org
* (C) HydroloGIS - www.hydrologis.com
*
* This library is free software; you can redistribute it and/or modify it under
* the terms of the GNU Library General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option) any
* later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more
* details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; if not, write to the Free Foundation, Inc., 59
* Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package org.jgrasstools.gears.utils.sorting;
import static org.jgrasstools.gears.libs.modules.JGTConstants.isNovalue;
import org.jgrasstools.gears.libs.monitor.LogProgressMonitor;
import org.jgrasstools.gears.libs.monitor.IJGTProgressMonitor;
/**
* Sorting of a double array with an array of objects following.
*
* @author Andrea Antonello (www.hydrologis.com)
*
*/
public class QuickSortAlgorithmObjects {
private double[] valuesToSort;
private int number;
private Object[] valuesToFollow;
private IJGTProgressMonitor monitor = new LogProgressMonitor();
public QuickSortAlgorithmObjects( IJGTProgressMonitor monitor ) {
if (monitor != null)
this.monitor = monitor;
}
/**
* Sorts an array of values and moves with the sort a second array.
*
* @param values the array to sort.
* @param valuesToFollow the array that should be sorted following the
* indexes of the first array. Can be null.
*/
public void sort( double[] values, Object[] valuesToFollow ) {
this.valuesToSort = values;
this.valuesToFollow = valuesToFollow;
number = values.length;
monitor.beginTask("Sorting...", -1);
monitor.worked(1);
quicksort(0, number - 1);
monitor.done();
}
private void quicksort( int low, int high ) {
int i = low, j = high;
// Get the pivot element from the middle of the list
double pivot = valuesToSort[(low + high) >>> 1];
// Divide into two lists
while( i <= j ) {
// If the current value from the left list is smaller then the pivot
// element then get the next element from the left list
while( valuesToSort[i] < pivot || (isNovalue(valuesToSort[i]) && !isNovalue(pivot)) ) {
i++;
}
// If the current value from the right list is larger then the pivot
// element then get the next element from the right list
while( valuesToSort[j] > pivot || (!isNovalue(valuesToSort[j]) && isNovalue(pivot)) ) {
j--;
}
// If we have found a values in the left list which is larger then
// the pivot element and if we have found a value in the right list
// which is smaller then the pivot element then we exchange the
// values.
// As we are done we can increase i and j
if (i <= j) {
exchange(i, j);
i++;
j--;
}
}
// Recursion
if (low < j)
quicksort(low, j);
if (i < high)
quicksort(i, high);
}
private void exchange( int i, int j ) {
double temp = valuesToSort[i];
valuesToSort[i] = valuesToSort[j];
valuesToSort[j] = temp;
if (valuesToFollow != null) {
Object tempFollow = valuesToFollow[i];
valuesToFollow[i] = valuesToFollow[j];
valuesToFollow[j] = tempFollow;
}
}
}