 |
AppletTalk.com
Java discussions newsgroups
|
| View previous topic :: View next topic |
| Author |
Message |
Vahe Musoyan
Guest
|
 Posted: Fri Oct 27, 2006 8:05 pm Post subject: sorting int[] in descending order |
 |
|
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? |
|
| Back to top |
|
 |
Patricia Shanahan
Guest
|
| Posted: Fri Oct 27, 2006 8:20 pm Post subject: Re: sorting int[] in descending order |
|
|
Vahe Musoyan wrote:
| Quote: | 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.
Option 1 involves a lot of coding. Options 2 and 3 each involve more
overhead than reversing the array after an ascending order sort.
If, for its other uses, this array is on the borderline between being
best represented by an int[] or an Integer[], then the descending sort
requirement might tip it over to Integer[], and you could do the sort
with descending order Comparator without any copying.
Patricia |
|
| Back to top |
|
|
Eric Sosman
Guest
|
| Posted: Fri Oct 27, 2006 8:37 pm Post subject: Re: sorting int[] in descending order |
|
|
Patricia Shanahan wrote On 10/27/06 11:20,:
| Quote: | 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 (AT) sun (DOT) com |
|
| Back to top |
|
|
Daniel Dyer
Guest
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
