I noticed a couple areas where yours could be improved efficiency wise and one potential bug:

That is a big improvement, especially fixing the bug. The redo instead of goto is so obvious ... yet I didn't see it.

I'm definitely a fan of jaredor's solution below

Me too. At least, jaredor's second solution. Which I'd missed till now.

I did see his original solution and my eyes zeroed in on this line:

my @sg = sort {$a<=>$b} uniq grep {defined} (@v2g{@$i}, min @$i);

[download]

There's a lot of potentially expensive processing going on in that one line. Repeating that every time around the outer loop of a large set of data smacked of "expensive".

By contrast, his second solution is almost magical in its simplicity and deserves elevating to tutorial.

I wouldn't mind betting that many of the graphing packages (and their authors) could learn a lot from that unremarkable looking piece of code.

then realized that there didn't need to be an identified element per subgraph...

Don't you just love understatement :)

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^3: how to find combine common elements of an array? by BrowserUk
in thread how to find combine common elements of an array? by ihperlbeg

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, details, 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, summary, 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.