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array index for new value

notorious
Novice

May 23, 2011, 12:28 PM

Post #1 of 7 (698 views)

array index for new value	Can't Post

Hi,

I have been trying to figure out how to do this, and cannot come up with a good solution.

I have a sorted Array with values like this:

18 13 11 10 9 7 4

I have a value of 15, and I want to figure out what the next highest number would be above 15.

For example, from 15, I want to be able to pull 18 out of the above sorted array as a result.

Can anyone point me out in the right direction with some pseudo code on how to do this with perl?

Thanks, Rob

miller
User

May 23, 2011, 1:35 PM

Post #2 of 7 (694 views)

Re: [notorious] array index for new value [In reply to]	Can't Post

The fact that the array is ordered doesn't have to effect the algorithm at all:

Code

use strict; 
use warnings; 
 
my @list = qw(18 13 11 10 9 7 4); 
 
my $num = 14; 
 
my $next = undef; 
for (@list) { 
	if ($_ > $num && (! defined $next || $_ < $next)) { 
		$next = $_; 
	} 
} 
 
print "$next\n";

miller
User

May 23, 2011, 1:43 PM

Post #3 of 7 (690 views)

Re: [miller] array index for new value [In reply to]	Can't Post

A cleaner method would probably be to use List::Util

Code

use List::Util qw(min); 
 
use strict; 
use warnings; 
 
my @list = qw(18 13 11 10 9 7 4); 
 
my $num = 14; 
 
my $next = min grep {$_ > $num} @list; 
 
print "$next\n";

- Miller

shawnhcorey
Enthusiast

May 23, 2011, 1:44 PM

Post #4 of 7 (689 views)

Re: [notorious] array index for new value [In reply to]	Can't Post

If the array is sorted, then you can use a binary search.

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notorious
Novice

May 23, 2011, 2:01 PM

Post #5 of 7 (685 views)

Re: [miller] array index for new value [In reply to]	Can't Post

Thanks miller. I will do it without the List::Utils module, since i need to distribute the script to machines, which have a very cut-down list of available modules and no access to the internet.

That helps, I was thinking of doing a similar method, but was not sure if there was any better method out there.

miller
User

May 23, 2011, 2:03 PM

Post #6 of 7 (683 views)

Re: [notorious] array index for new value [In reply to]	Can't Post

List::Util is part of core.

- Miller

notorious
Novice

May 23, 2011, 2:10 PM

Post #7 of 7 (682 views)

Re: [miller] array index for new value [In reply to]	Can't Post

Yes, but the script has to work with an even further cut-down customized distribution, which does not contain that module.

Thanks.

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