Mega Code Archive
A quick sort demonstration algorithm
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/*
* The remainder of this file is borrowed from: @(#)QSortAlgorithm.java 1.3 29
* Feb 1996 James Gosling
*
* Copyright (c) 1994-1996 Sun Microsystems, Inc. All Rights Reserved.
*
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*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
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*
* THIS SOFTWARE IS NOT DESIGNED OR INTENDED FOR USE OR RESALE AS ON-LINE
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*/
/**
* A quick sort demonstration algorithm SortAlgorithm.java
*
* @author James Gosling
* @author Kevin A. Smith
* @version @(#)QSortAlgorithm.java 1.3, 29 Feb 1996
*/
/**
* This is a generic version of C.A.R Hoare's Quick Sort algorithm. This will
* handle arrays that are already sorted, and arrays with duplicate keys. <BR>
*
* If you think of a one dimensional array as going from the lowest index on the
* left to the highest index on the right then the parameters to this function
* are lowest index or left and highest index or right. The first time you call
* this function it will be with the parameters 0, a.length - 1.
*
* @param a
* a string array
* @param lo0
* left boundary of array partition
* @param hi0
* right boundary of array partition
*/
public class Sort {
void QuickSort(String a[], int lo0, int hi0) {
int lo = lo0;
int hi = hi0;
String mid;
if (hi0 > lo0) {
/*
* Arbitrarily establishing partition element as the midpoint of the
* array.
*/
mid = a[(lo0 + hi0) / 2];
// loop through the array until indices cross
while (lo <= hi) {
/*
* find the first element that is greater than or equal to the
* partition element starting from the left Index.
*/
while ((lo < hi0) && (a[lo].compareTo(mid) < 0))
++lo;
/*
* find an element that is smaller than or equal to the
* partition element starting from the right Index.
*/
while ((hi > lo0) && (a[hi].compareTo(mid) > 0))
--hi;
// if the indexes have not crossed, swap
if (lo <= hi) {
String t = a[hi];
a[hi] = a[lo];
a[lo] = t;
++lo;
--hi;
}
}
/*
* If the right index has not reached the left side of array must
* now sort the left partition.
*/
if (lo0 < hi)
QuickSort(a, lo0, hi);
/*
* If the left index has not reached the right side of array must
* now sort the right partition.
*/
if (lo < hi0)
QuickSort(a, lo, hi0);
}
}
}
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