Re: Verifying a list is alphabetized

From:
Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 03 Dec 2011 09:02:47 -0500
Message-ID:
<jbda6g$nh$1@dont-email.me>
On 12/3/2011 7:44 AM, Eric Sosman wrote:

On 12/2/2011 7:54 PM, Arne Vajh?j wrote:

On 11/30/2011 11:05 AM, Knute Johnson wrote:

On 11/30/2011 7:52 AM, laredotornado wrote:

I'm using Java 1.6. Given a java.util.List of Strings, what is the
quickest way to verify that the list is sorted in ascending order?

Thanks, - Dave


If it could possibly unsorted, I'd just sort it. How big is this list
anyway?


If it is small it does not matter.

But I would not recommend an O(nlogn) solution for a O(n)
problem unless there is a note in 72 pt red blinking
on top of it.


What is the big-Oh complexity of Collections.sort(List<String>)
on an already-sorted list?
[...]


     Just for fun, I tried it out. For a twenty-element ArrayList,
Vector, Stack, or LinkedList, Collections.sort() uses

     19 comparisons if the List is in strictly increasing order,

     19 comparisons if the List is in non-decreasing order but
        with equal elements,

     19 comparisons if the List is in strictly decreasing order,

     70 comparisons (!) if the List is in non-increasing order but
       with equal elements. (Likely data-dependent.)

     Conclusion: I think using the color red for the 72-point
blinking note is overkill. Try white, on a white background. :)

--
Eric Sosman
esosman@ieee-dot-org.invalid

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