Re^3: how to find combine common elements of an array?

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);
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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.

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Re^4: how to find combine common elements of an array? by wind (Priest) on Apr 26, 2011 at 02:23 UTC
Don't you just love understatement :) Aye, I'm very much in awe of his use of references in the solution. Would just never think to use uniq in that way. I actually noticed another potential problem with your and my later solution. `for my $i (0..$#array)` doesn't recalculate the max value with each iteration. It isn't a problem given it does for the inner loop, but it could potentially lead to issues in a different algorithm, so glad I noticed this.	[reply] [d/l]

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Re^4: how to find combine common elements of an array?
by wind (Priest) on Apr 26, 2011 at 02:23 UTC

Don't you just love understatement :)

Aye, I'm very much in awe of his use of references in the solution. Would just never think to use uniq in that way.

I actually noticed another potential problem with your and my later solution. for my $i (0..$#array) doesn't recalculate the max value with each iteration. It isn't a problem given it does for the inner loop, but it could potentially lead to issues in a different algorithm, so glad I noticed this.

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