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

comment on

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

interesting. the incorrect solution that your toolsmith provided has inspired me to come up with a variation which i think is correct:

my @shuffled = map {$_->[0]} sort { $a->[1] <=> $b->[1]} map {[$_, rand(1)]} @array;

kind of a 'randomized schwartzian transform' approach.

it benchmarks slightly faster than the standard Fisher-Yates shuffle but not quite as fast as the broken version. mine and Fisher-Yates are both going to be linear with the size of the array and you really can't do any better than that and still have a correct solution.

i'm honestly baffled as to why the broken one runs so quickly. my best guess is that getting different values on each comparison in some cases confuses qsort to the point where it thinks it's done before it really is. alternatively though it seems like if you get the wrong series of random numbers, it could make qsort take even longer than normal.

anders pearson

In reply to Re: When the Best Solution Isn't by thraxil
in thread When the Best Solution Isn't by sauoq

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?

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

    How do I use this? | Other CB clients
    Other Users?
    Others chanting in the Monastery: (4)
    As of 2019-12-13 20:34 GMT
    Find Nodes?
      Voting Booth?

      No recent polls found