How are you?
I have a qsort() question. Can you do qsort only on a part of an array (not the entire array).
For example if I have:
and I want to sort myArray between entries 10 and 20 only (and not touch the array between 0...9 and 21...49), would that be possible.
What would be the syntax of such a sort.
Thank you very much.
yes you can where you will send the lower index as 10 and higher index as 20. Here is a smaple code for q sort.
class QSortAlgorithm extends SortAlgorithm
/** 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.
* 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;
// pause for redraw
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] < mid ) )
/* find an element that is smaller than or equal to
* the partition element starting from the right Index.
while( ( hi > lo0 ) && ( a[hi] > mid ) )
// if the indexes have not crossed, swap
if( lo <= hi )
swap(a, 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)
T = a[i];
a[i] = a[j];
a[j] = T;
public void sort(int a) throws Exception
QuickSort(a, 0, a.length - 1);