Solved

how to shuffle an array in perl

Posted on 2006-10-23
4
1,243 Views
Last Modified: 2008-09-07
Hi experts. I am trying to make a program with perl to shuffle an array. It is basically a card game. I am using pop, shift and push functions in order to do this but not too sure how. Help would be greatly appreciated thanks.
0
Comment
Question by:micromarch
  • 2
  • 2
4 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 500 total points
ID: 17792294
perldoc -q shuffle
Found in pods/perlfaq4.pod
       How do I shuffle an array randomly?

       If you either have Perl 5.8.0 or later installed, or if you have
       Scalar-List-Utils 1.03 or later installed, you can say:

           use List::Util 'shuffle';

               @shuffled = shuffle(@list);

       If not, you can use a Fisher-Yates shuffle.

           sub fisher_yates_shuffle {
               my $deck = shift;  # $deck is a reference to an array
               my $i = @$deck;
               while ($i--) {
                   my $j = int rand ($i+1);
                   @$deck[$i,$j] = @$deck[$j,$i];
               }
           }

           # shuffle my mpeg collection
           #
           my @mpeg = <audio/*/*.mp3>;
           fisher_yates_shuffle( \@mpeg );    # randomize @mpeg in place
           print @mpeg;

       Note that the above implementation shuffles an array in place, unlike
       the List::Util::shuffle() which takes a list and returns a new shuffled
       list.

       You've probably seen shuffling algorithms that work using splice, ran-
       domly picking another element to swap the current element with

           srand;
           @new = ();
           @old = 1 .. 10;  # just a demo
           while (@old) {
               push(@new, splice(@old, rand @old, 1));
           }

       This is bad because splice is already O(N), and since you do it N
       times, you just invented a quadratic algorithm; that is, O(N**2).  This
       does not scale, although Perl is so efficient that you probably won't
       notice this until you have rather largish arrays.
0
 
LVL 2

Author Comment

by:micromarch
ID: 17792309
yeh that works but my co-workers want me to use push,shift and pop.
0
 
LVL 84

Expert Comment

by:ozo
ID: 17792380
why would they want you to do that?
would your co-workers allow you to use an auxilliary array?
you could implement the slice using push and shift
0
 
LVL 2

Author Comment

by:micromarch
ID: 17792827
what do they mean by returning an element for example the pop function? i can return the element i removed somewheres else?
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
array6 challenfge 6 83
File.WriteAllLines problem at random C# ASP.NET 6 66
wordappend challenge 8 149
Export Table to CSV - Access to CSV - using python 18 100
Whether you’re a college noob or a soon-to-be pro, these tips are sure to help you in your journey to becoming a programming ninja and stand out from the crowd.
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
An introduction to basic programming syntax in Java by creating a simple program. Viewers can follow the tutorial as they create their first class in Java. Definitions and explanations about each element are given to help prepare viewers for future …
In this fourth video of the Xpdf series, we discuss and demonstrate the PDFinfo utility, which retrieves the contents of a PDF's Info Dictionary, as well as some other information, including the page count. We show how to isolate the page count in a…

867 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

21 Experts available now in Live!

Get 1:1 Help Now