Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
A couple of comments:

1) the open || die statement should actually be

open IN, $infile or die "Can't open input file: $!";
For reasons of precedence.

2) Here are some faster algorithms. One way is to use a hash to record which characters you've already placed into your substitution string. Here's the main loop:

my %set; my $substit = ""; for (1..26) { my $randchar; do { $randchar = chr((int rand 26) + 65) } while $set{$randchar}++; $substit .= $randchar; }
This way you don't have to do a search through the string each time.

And here's an even better way of doing it: build a random permutation of the alphabet string. To do this, we'll actually need an array:

my @alpha = split //, "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
Now we set another array equal to this one, then call the random shuffle algorithm on it:
my @crypt = @alpha; fisher_yates_shuffle(\@crypt);
which shuffles the array in place. Now all you need to do is get back the substitution string:
my $substit = join '', @crypt;
Here's the definition of the fisher_yates_shuffle sub:
sub fisher_yates_shuffle { my $array = shift; for (my $i = @$array; --$i; ) { my $j = int rand ($i+1); next if $i == $j; @$array[$i, $j] = @$array[$j, $i]; } return join '', @$array; }
(Taken directly from perlfaq4.)

I did some benchmarking on these, and here's what I got:

Benchmark: timing 5000 iterations of orig, f_yates, hash... orig: 33 secs (23.60 usr 0.00 sys = 23.60 cpu) f_yates: 5 secs ( 2.88 usr 0.00 sys = 2.88 cpu) hash: 13 secs ( 5.68 usr 0.00 sys = 5.68 cpu)
where "orig" is the one you posted, "f_yates" is the one using fisher_yates_shuffle, and "hash" is the one using a hash to record seen characters.

If I've messed anything up, let me know.


In reply to RE: Cryptogram Generator by btrott
in thread Cryptogram Generator by Elihu

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others pondering the Monastery: (9)
    As of 2015-07-02 02:20 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









      Results (25 votes), past polls