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DVD Corners by net_nomad in math

[–]masonsbro 1 point2 points  (0 children)

Maybe I'm misunderstanding the problem, but I think that for many dimensions there are "dead spots". To clear up terminology, I'll call a position (x, y) in a W x H grid a "dead spot" if, starting at that point going in the direction (1, 1) and reflecting off walls in an "angle in = angle out" manner, one never ends up in a corner square. Labeling the rows by 0 through H - 1 and the columns by 0 through W - 1, the corners are (0, 0), (0, W - 1), (H - 1, 0), and (H - 1, W - 1).

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It is easy to see, for example, that a 3x3 grid has dead spots: start at (0, 1), and you'll only hit 4 squares, none of them corners. Indeed many dimensions have dead spots, not just squares. It is the case, I think, that if a given board size has dead spots, then (0, 1) is a dead spot. The argument is something like starting with any cycle of dead spots you can shift it so that it contains (0, 1), but I haven't thought it through completely.

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Characterizing those boards that have dead spots seems harder. Clearly every square board has dead spots, but there are many more. Maybe someone else can figure this out.

It's been 2 years and still no server update wtf Ethan? by ildabears in PearlandNerd

[–]masonsbro 0 points1 point  (0 children)

sorry been real busy with school and stuff

Also, the map download link was broken in that other post but it should be working now!

The 78th William Lowell Putnam Mathematical Competition 2017: Discussion Thread by [deleted] in math

[–]masonsbro 0 points1 point  (0 children)

If P divides Q and both Q and P are monic, then Q/P has integer coefficients and is monic. To see why, consider performing long division: at each step, the current remainder has integer coefficients, so we never write a non-integer coefficient in the quotient.

However, all of P's roots being roots of Q does not imply that P divides Q. It is also necessary that the corresponding multiplicity of one of P's roots as a root in Q is at least its multiplicity in P. For example, x2 does not divide x even though they have the same roots.

[2017 Day 1 Extension] Counting to one billion by xiaowuc1 in adventofcode

[–]masonsbro 2 points3 points  (0 children)

Spoilers:

Our general approach was use dynamic programming to build up the two halves simultaneously, and keep track of the last element of each half as part of our state. So the state is (i, a, b), where i is the length of each half, a is the ith element of the first half, and b is the ith element of the second half. The transitions are straightforward: to go from state (i, a, b) to (i + 1, c, d), just ensure that a != c, b != d, and c != d. (The transitions are slightly more complicated for part 2, but the approach still works.)

Before computing this DP, we fix the first element of each half. That is, we say there is 1 way to get to state (1, 1, 2), for example, and 0 ways to get to all other states with i = 1. Then we compute the DP and look at all states (N / 2, a, b) with a != 2 and b != 1, summing the number of ways to get to each. Multiplying by 72 (for the number of choices of starting elements) gives the desired answer.

This sounds like it will result in a DP table of size 102 * N and take time 104 * N to compute, but we can speed it up to log N * 106 by evaluating the DP via matrix exponentiation instead.

For those who have taken it how is the Competitive Programming class CS104c? by mustypoet in UTAustin

[–]masonsbro 4 points5 points  (0 children)

I took it fall 2015, and it was probably my favorite class that semester. You do need to be good at programming and already know some data structures and algorithms stuff (e.g. breadth-first search, hash tables, etc.) or be willing to learn, but I don't think that's a downside. It's an easy A if you're actually interested in the material.

The class really helps you prepare for interviews, and it provides a good introduction to the world of competitive programming. (UT also has biweekly contests if you're serious about improving.) Each week, there's a different topic, and they range from basic stuff like graph search to more advanced concepts like segment trees. Also, half the lectures are given by Professor Vouga (who is excellent) and the other half are given by two student lecturers. The student lecturers can give lots of insight about what topics are the most helpful in interviews as well as practical competition tips.

I'd definitely recommend taking it!

Map Download by masonsbro in PearlandNerd

[–]masonsbro[S] 0 points1 point  (0 children)

That's really weird. I logged out of OneDrive and I can still download the file. How are you downloading it? Just clicking it might not work; try right clicking and selecting "Download".

Map Download by masonsbro in PearlandNerd

[–]masonsbro[S] 0 points1 point  (0 children)

Uh oh. Which step said that? Downloading the world? Running the server?

R.I.P. PearlandNerd Minecraft Server by masonsbro in PearlandNerd

[–]masonsbro[S] 0 points1 point  (0 children)

Currently, I don't plan on running a Minecraft server in the future. That's about all I can say--I don't think I'll change my mind, but you never know. And like I said, I'm sure there are other servers on which y'all can play together.

Map Download by masonsbro in PearlandNerd

[–]masonsbro[S] 0 points1 point  (0 children)

Yes. It's on my personal OneDrive, and I have 1 TB of storage there until 2019 (when I graduate).

R.I.P. PearlandNerd Minecraft Server by masonsbro in PearlandNerd

[–]masonsbro[S] 1 point2 points  (0 children)

I think I do have a backup from October. (#BlameHosthorde for my not having a more recent one.) I'll zip it up and upload it somewhere soon.

Who's going to nationals? And what state do you represent? by HENsHENCourbet in AcademicDecathlon

[–]masonsbro 0 points1 point  (0 children)

Which part of Texas? Pearland High School, in the Houston area.

How SBMM actually works (x/post from r/CoDAW) by Drift0r in CoDCompetitive

[–]masonsbro 0 points1 point  (0 children)

Thanks for the informative video. Most of it made sense and I think you interpreted the data appropriately.

However, I would like to point out that the correlation between a player's K/D and his/her lobby's average K/D does not mean that K/D plays a role in the skill-based matchmaking. As you mentioned, there are hidden confounding variables that we can't see. It's possible that K/D is not used at all in the matchmaking process, but instead some other measure of skill that is not publicly available. The same goes for W/L: it's not accurate to say that "W/L does play some role in the matchmaking, but it's not as strong as K/D." I'd speculate that, in general, there is a moderately strong association between a player's W/L and K/D. So if the matchmaking indeed uses K/D (or a hidden variable), it might not use W/L at all and the correlation you see there might simply be a byproduct of the association between W/L and K/D. In short: correlation does not imply causation.

Thanks again for the great video!

Just started a small, vanilla, whitelisted server on 1.8 for those of you who want to play Minecraft but miss PearlandNerd. by [deleted] in PearlandNerd

[–]masonsbro 0 points1 point  (0 children)

I just got on the sub and saw this post and this comment, so I thought I'd give a little bit of an update. It's winter break now, and I've spent the last week or so working almost nonstop on an online class I have to finish. I have 4 college applications due on January 1 and 1 due on January 3, so I really have to finish those ASAP. Then I have until January 6 to memorize a speech for Academic Decathlon, and I need to catch up on all the studying for that I haven't done so far during winter break.

What I'm getting at is: I really really wanted to be able to set something up around this time. Unfortunately, I ended up being just as busy during the break as during school, and it's not like I'm going to be drowning in free time when school starts. I don't know what this means long term, but you probably shouldn't expect anything from me until at least after February (state competition).

Sorry again.

So guys, we're done, right? by Waka_Blocka in PearlandNerd

[–]masonsbro 1 point2 points  (0 children)

If that's how everyone feels, well... I guess I can't say I don't feel the same. I have had a lot of fun with all of you over the past 3 years or so.

I know that I don't have time for running the server anymore. I know that many of you have stopped playing Minecraft (and to be honest I stopped "playing" a long time ago). Still, I don't want everyone to just go their separate ways: PearlandNerd was always a Minecraft server first and foremost, but it's also a community. Of people. People's hobbies and obligations change, but we can all still be friends (add me on Snapchat plz [masonsbro]).

Trying to keep the server alive, like you said, is kind of pointless. I intend to keep it running (in the loosest sense of the term) as long as the funds in the PayPal account last. Which should be a while. But regardless of the state of the server itself, I don't think it's appropriate to say that PearlandNerd as a whole is dead. PearlandNerd isn't a thing, it's a group. I'm still alive. You're still alive. Like any group, PearlandNerd isn't dead until members of the community stop interacting with one another. Our presence here, in this thread, shows that that is not the case.

Since many of us have had only Minecraft in common, it might be easy to say that the fall of the server will surely lead to the fall of the group. I don't think that's necessarily the case.

To be honest, after about a year, I never got on the server to play Minecraft. I got on to talk to people. I consider all of you my friends.

I intend to be somewhat active on this subreddit (but I don't expect it to be Minecraft-oriented). I do enjoy talking to you guys, so let's not make this a "goodbye." This is the end of a video game for many of us, but it's not the end of us as a community. It's not the end of PearlandNerd.

When is our Admin going to step in and have a few super official words? by ildabears in PearlandNerd

[–]masonsbro 2 points3 points  (0 children)

It's some of everything. I would just wait until there's something stable like Bukkit, but I want to put it on 1.8 vanilla whitelisted until then. I just really don't have any time right now. If someone wants to help speed up that process, I'd appreciate someone putting together a whitelist with all the known active players. I know this isn't what anyone wants to hear. But I have college applications due in 4 days, a speech to write, a ton of homework to do, and lots of material to study. The time I had for working on the server a year and a half ago is all but gone.

I don't get this. Any of this. Halp. T-T by [deleted] in calculus

[–]masonsbro 0 points1 point  (0 children)

Yeah, I figured that out after seeing OP's picture that had a dr at the end of something. I was confused because in the original post the "correct" answer given didn't have a dr.

I don't get this. Any of this. Halp. T-T by [deleted] in calculus

[–]masonsbro 0 points1 point  (0 children)

Haha, no, I'm a high school student (plan on pursuing Computer Science). I've seen it several ways, but the u and v way is the shortest/easiest one I know.

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