svn-gvsig-desktop / tags / v1_0_2_Build_897 / libraries / libCq CMS for java.old / src / org / cresques / filter / QuickSort.java @ 10444
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/*
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* Cresques Mapping Suite. Graphic Library for constructing mapping applications.
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*
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* Copyright (C) 2004-5.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,USA.
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*
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* For more information, contact:
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*
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* cresques@gmail.com
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*/
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package org.cresques.filter; |
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/**
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* Ordenaci?n de los elementos de un vector
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* @author Robert Sedgewick and Kevin Wayne
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*/
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public class QuickSort { |
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private long comparisons = 0; |
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private long exchanges = 0; |
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/***********************************************************************
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* Quicksort code from Sedgewick 7.1, 7.2.
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***********************************************************************/
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public void quicksort(int[] a) { |
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quicksort(a, 0, a.length - 1); |
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} |
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public void quicksort(int[] a, int left, int right) { |
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if (right <= left) {
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return;
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} |
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int i = partition(a, left, right);
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quicksort(a, left, i - 1);
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quicksort(a, i + 1, right);
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} |
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private int partition(int[] a, int left, int right) { |
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int i = left - 1; |
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int j = right;
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while (true) { |
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// find item on left to swap
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while (less(a[++i], a[right]))
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; |
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// find item on right to swap
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while (less(a[right], a[--j]))
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if (j == left) {
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break;
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} |
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// check if pointers cross
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if (i >= j) {
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break;
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} |
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exch(a, i, j); |
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} |
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// swap with partition element
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exch(a, i, right); |
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return i;
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} |
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// is x < y ?
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private boolean less(int x, int y) { |
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comparisons++; |
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return (x < y);
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} |
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// exchange a[i] and a[j]
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private void exch(int[] a, int i, int j) { |
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exchanges++; |
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int swap = a[i];
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a[i] = a[j]; |
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a[j] = swap; |
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} |
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} |