Re: sorting int[] in descending order

From:

Eric Sosman <Eric.Sosman@sun.com>

Newsgroups:

comp.lang.java.help

Date:

Fri, 27 Oct 2006 11:37:38 -0400

Message-ID:

<1161963459.590384@news1nwk>

Patricia Shanahan wrote On 10/27/06 11:20,:

Vahe Musoyan wrote:

What's the best way to sort an array of integers in descending order?
I know that one can sort in ascending order and reverse the array. Is
there any other/better way?

There are other ways, but I don't think any of the ones I know are better:

1. Write your own quicksort descending order implementation.

2. Create an Integer array with the values from the int[] and
Arrays.sort it using a supplied Comparator that reverses the
a.compareTo(b) result.

3. Replace each element of the array with the result of subtracting it
from -1, sort normally, then repeat the replacement operation. The
initial subtraction maps the largest value to the smallest, smallest to
largest etc. The final subtraction restores the original values.
[...]

4. "Count backwards:" sort the array in ascending order, but
"reflect" the index whenever you access it. Most crudely,
replace array[i] with array[array.length-1-i]. Somewhat more
smoothly, replace

for (int i = 0; i < array.length; ++i)

with

for (int i = array.length; --i >= 0; )

--
Eric.Sosman@sun.com