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/*
* Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* A quick sort demonstration algorithm
* SortAlgorithm.java
*
* @author James Gosling
* @author Kevin A. Smith
*/
public class QSortAlgorithm extends SortAlgorithm {
/**
* A version of pause() that makes it easier to ensure that we pause
* exactly the right number of times.
*/
private boolean pauseTrue(int lo, int hi) throws Exception {
super.pause(lo, hi);
return true;
}
/** 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 an integer array
* @param lo0 left boundary of array partition
* @param hi0 right boundary of array partition
*/
void QuickSort(int a[], int lo0, int hi0) throws Exception {
int lo = lo0;
int hi = hi0;
int 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) && pauseTrue(lo0, hi0) && (a[lo] < mid)) {
++lo;
}
/* find an element that is smaller than or equal to
* the partition element starting from the right Index.
*/
while ((hi > lo0) && pauseTrue(lo0, hi0) && (a[hi] > mid)) {
--hi;
}
// if the indexes have not crossed, swap
if (lo <= hi) {
swap(a, lo, hi);
++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);
}
}
}
private void swap(int a[], int i, int j) {
int T;
T = a[i];
a[i] = a[j];
a[j] = T;
}
@Override
public void sort(int a[]) throws Exception {
QuickSort(a, 0, a.length - 1);
}
}
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