Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl-Sensitive Sunglasses
 
PerlMonks  

comment on

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

We can just use the shuffle algorithm slightly modified to suit our needs :

use Inline C => <<'END_OF_C_CODE'; void cderange(SV* array_ref) { AV* array; I32 index, i; SV** sv_1, **sv_2; SV* sv_temp; if (! SvROK(array_ref)) croak("array_ref is not a reference"); srand(time( NULL )); array = (AV*)SvRV(array_ref); index = av_len(array); for (; index; index--) { i = (I32) (rand() % (index)); sv_1 = av_fetch(array, index, 0); sv_2 = av_fetch(array, i, 0); sv_temp = *sv_1; *sv_1 = *sv_2; *sv_2 = sv_temp; } return; } END_OF_C_CODE sub derange { my $first = $_[0]; cderange \@_; if( $first eq $_[0] ){ ($_[0], $_[1]) = ($_[1], $_[0]) } return @_; }

This is fast, but don't work very well with very big arrays (size over RANDMAX, usually 32000).

--
Jedaļ

In reply to Re^4: Derangements iterator by Anonymous Monk
in thread Derangements iterator by tye

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!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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 perusing the Monastery: (1)
    As of 2021-04-17 02:31 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      No recent polls found

      Notices?