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*
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/*
* This source code is provided to illustrate the usage of a given feature
* or technique and has been deliberately simplified. Additional steps
* required for a production-quality application, such as security checks,
* input validation and proper error handling, might not be present in
* this sample code.
*/
/**
* 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);
}
}