/* * @(#)EQSortAlgorithm.java 1.0 95/06/26 Jim Boritz * * Copyright (c) 1995
UBC Microsystems, Inc. All Rights Reserved. * * Permission to use, copy,
modify, and distribute this software * and its documentation for
NON-COMMERCIAL purposes and without * fee is hereby granted provided that
this copyright notice * appears in all copies. Please refer to the file
"copyright.html" * for further important copyright and licensing
information. * * UBC 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. UBC SHALL NOT BE LIABLE FOR * ANY
DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR *
DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. */ /** * An enhanced quick
sort demonstration algorithm * SortAlgorithm.java, Thu Oct 27 10:32:35 1994
* * @author Jim Boritz * @version 1.0, 26 Jun 1995 */ /** * 19 Feb 1996:
Fixed to avoid infinite loop discoved by Paul Haberli. * Misbehaviour
expressed when the pivot element was not unique. * -Jason Harrison * * 21
Jun 1996: Modified code based on comments from Paul Haeberli, and * Peter
Schweizer (Peter.Schweizer@mni.fh-giessen.de). * Used Daeron Meyer's
(daeron@geom.umn.edu) code for the * new pivoting code. - Jason Harrison * *
09 Jan 1998: Another set of bug fixes by Thomas Everth (everth@wave.co.nz) *
and John Brzustowski (jbrzusto@gpu.srv.ualberta.ca). */ class
EQSortAlgorithm extends SortAlgorithm { void brute(int a[], int lo, int hi)
throws Exception{ if ((hi-lo) == 1) { if (a[hi] < a[lo]) { int T = a[lo];
a[lo] = a[hi]; a[hi] = T; pause(); } } if ((hi-lo) == 2) { int pmin = a[lo]
< a[lo+1] ? lo : lo+1; pmin = a[pmin] < a[lo+2] ? pmin : lo+2; if (pmin !=
lo) { int T = a[lo]; a[lo] = a[pmin]; a[pmin] = T; pause(); } brute(a, lo+1,
hi); } if ((hi-lo) == 3) { int pmin = a[lo] < a[lo+1] ? lo : lo+1; pmin =
a[pmin] < a[lo+2] ? pmin : lo+2; pmin = a[pmin] < a[lo+3] ? pmin : lo+3; if
(pmin != lo) { int T = a[lo]; a[lo] = a[pmin]; a[pmin] = T; pause(); } int
pmax = a[hi] > a[hi-1] ? hi : hi-1; pmax = a[pmax] > a[hi-2] ? pmax : hi-2;
if (pmax != hi) { int T = a[hi]; a[hi] = a[pmax]; a[pmax] = T; pause(); }
brute(a, lo+1, hi-1); } } void sort(int a[], int lo0, int hi0) throws
Exception { int lo = lo0; int hi = hi0; pause(lo, hi); if ((hi-lo) <= 3) {
brute(a, lo, hi); return; } /* * Pick a pivot and move it out of the way */
int pivot = a[(lo + hi) / 2]; a[(lo + hi) / 2] = a[hi]; a[hi] = pivot;
while( lo < hi ) { /* * Search forward from a[lo] until an element is found
that * is greater than the pivot or lo >= hi */ while (a[lo] <= pivot && lo
< hi) { lo++; } /* * Search backward from a[hi] until element is found that
* is less than the pivot, or hi <= lo */ while (pivot <= a[hi] && lo < hi )
{ hi--; } /* * Swap elements a[lo] and a[hi] */ if( lo < hi ) { int T =
a[lo]; a[lo] = a[hi]; a[hi] = T; pause(); } } /* * Put the median in the
"center" of the list */ a[hi0] = a[hi]; a[hi] = pivot; /* * Recursive calls,
elements a[lo0] to a[lo-1] are less than or * equal to pivot, elements
a[hi+1] to a[hi0] are greater than * pivot. */ sort(a, lo0, lo-1); sort(a,
hi+1, hi0); } void sort(int a[]) throws Exception { sort(a, 0, a.length-1);
} }