Computer Science

1:42 AM

@vzn you have asked emab and probably me about detecting "communities" in EEG.

Where emab answered and I posted 2 links to him asking whether we talk about the same thing.

So, now, do you have your answers?

@Gilles very good point on meta. Is this a thread to work out some policy? Share thoughts? Ask about those questions? Like "should we change input to help solve the problem not just do someones homework"?

Or just indication to stop bouncing such questions to reference ones?

vzn

@EvilJS are you talking about the Fallani and Bullmore papers? yes saw/ browsed them, they are interesting.

2:23 AM

@vzn yes, ok, probably nothing to add

6 hours later…

Raphael

8:24 AM

@EvilJS You can always post a request on Meta Stack Exchange but I think chances are limited. What do you have in mind?

2 hours later…

Raphael

10:44 AM

@D.W. I like your answer to the homework meta question (thank @Gilles for asking it). However, it exposes a cute dichotomy: we ask people to post things that are helpful to others, but we also ask them to be very specific about their own problems with their homework.

Isn't, arguably, the plain problem dump the most "useful" for other with the same task? The answer lies, of course, in how we define "useful". Maybe you want to expand on that.

Gilles

@EvilJS my primary goal was to have guidance to offer to people who ask homework questions

but our homework policy is old, wasn't particularly consensual, and we aren't really following it

so a discussion of the policy may well erupt

@Raphael yes

that's one of the problems I have against both the closure of here's-my-homework questions and hint-only answers

I think we should close non-teachable homework dumps (straightforward application of the obvious definition/theorem) and answer others. But 1. it isn't an easy distinction to explain and 2. I get the impression that mine is a minority view.

Raphael

11:07 AM

@Gilles I think teachable homework questions are already well accepted; we may disagree on what exactly "teachable" means.

Good call on collecting advice for askers, in any case. It was long overdue. Once the answers stabilize, I'll integrate it into our homework dump default comments.

Jeff Teoh

12:03 PM

Hey

1 hour later…

1:13 PM

@JeffTeoh hey

1:49 PM

@Raphael forcexample there was some kind of disagreement about editing old posts - not preferable because it flows them to active, preferable to have corrected version.

But there are badges for necromancy, editing and even points for new users per edit, so summing every "profit" it just directs new users to dig up.

$m^2 - m + n^2 - n + mn + 1$ in asymptotic notation would be $O(m^2 + n^2)$ or $O(m^2 + n^2 + mn)$ ?

@Raphael so from the new users perspective, who might love badges (quite seriously, people actually do like them even if they do not care that much). "I want a special badge" - this was a quote, too late for adding ", anyway from small tour, meta which they do not read, but their profile, which they do, shows some shinny objects, and prequisites...

Q: Worst case time complexity , please check whether my solution is correct?

-2

A list of n strings, each of length n, is sorted into lexicographic order using the merge-sort algorithm. The worst case running time of this computation is __________. $O(n log n)$ $O(n^2 log n)$ $O(n^2 +log n)$ $O(n^2)$ My attempt: If we are used in-place merge sort , then time complexit...

algorithm-analysis runtime-analysis sorting

This one's back from the dead as well. OP made a useless edit.

@Auberon if you included both n^2 and m^2 it would imply that mn might have the same order?

@Auberon wow, no, on closed one self edit?

2:09 PM

@EvilJS Maybe for some edit badge.

vzn

2:45 PM

@EvilJS re gender differences in language, new study, finds large difference/ high predictibility on facebook! sciencedaily.com/releases/2016/05/160525161919.htm

Q: How to compute the sum of this series involving golden ratio, efficiently?

@vzn it is very cool, wow, 65k users, 10m messages, the sample was large enough in any possible sense, Thank you.

Did it said really 90%?

3 hours later…

Bounty!

5:39 PM

Definitions Let $\tau$ be a function on natural numbers defined as $\tau(n)=\lceil n*\phi^2\rceil$ where $n$ is some natural number and $\phi=\frac{1+\sqrt{5}}{2}$ is the golden ratio. This series can also be looked up here : A004957, with first few terms being $3,6,8,11,14...$ . Let $t$ be the...

time-complexity number-theory

2 hours later…

7:52 PM

If user asks the question, then deletes it, then asks another one - this is no longer in "first post queue"?

2 hours later…

9:41 PM

@Raphael That's a good point. It brings to mind the adage "give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime"; giving a person a fish (a complete answer to their homework question) might feel useful on first glance, but in the long run it's not useful (in the long run it doesn't help them understand the material better or get better at being able to solve these kinds of problems on their own).

@D.W. awesome insight. But what next? Should we change OP's data to answer the question? Generalize? Strip to the core of the problem? I assume the users will disagree, since they are in fast need to have it done and they do not see a big picture.

Change OP's data? You mean, like changing the problem a little bit and showing how to solve a related but slightly different problem?

@D.W. yes, to make sure that no copy-paste will solve the problem.

That's an interesting idea. It seems like it might be a nice way to help some people. I wonder whether they would appreciate it.

It might be fun to give it a try and see what kinds of reactions it gets!

Not really, no. It will not be appreciated by all of them, but it will make question helpful for future users or we will get a filter to tell apart learners from problem dumpers ;)

9:53 PM

Heh, you are right about that!

I have seen such answers already, some were greatful and they applied what they have learned and the others just abandoned the question.

BTW sorry for several comments in row mess - I will clean them after OP reads them.

Sounds like a nice solution!

Would questions involving linear programming belong on cs.se?

10:27 PM

@Auberon linear integer programming? Optimization? Simplex?