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Steve Ballmer's incorrect binary search interview question

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Re: Steve Ballmer's incorrect binary search interview question

#241

Post by quuxplusone »

gowld wrote: post #233
ckemere wrote: post #156

I really am curious about the Nash equilibrium solution. I assume that as a commenter has mentioned, for the guesser it involves returning random numbers near the binary search. But I’m curious if for the picker it involves a uniform or non uniform initial distribution?? I’m sure someone on HN knows/can explain?

I don't see how Ballmer randomly guessing a number and candidate doing binary search would NOT be Nash Equilibrium. For anything else, the candidate has a strategy of "guessing a trick number", and Ballmer has a strategy of "not choosing a trick number". The candidate can't force Ballmer to try to be tricky.

"Candidate always starts by guessing 50" can't possibly be part of a Nash equilibrium, since then Ballmer would never ever choose 50 as his secret number. (And indeed, he says as much in the linked video.) And if he'll never choose 50, then it's obviously silly for the candidate to waste a guess on it... and so on. Nash equilibria are usually (always?) located at mixed strategies.

Re: Steve Ballmer's incorrect binary search interview question

#242

Post by SonOfLilit »

HarryHirsch wrote: post #174
SonOfLilit wrote: post #152

Earlier quoted context omitted.

Downvoted for jumping from legitimate criticism of her interview methodology to very personal and completely baseless accusations. This is not the internet I want to live in.

This is not the internet I want to live in Storytime! In a previous workplace a disagreement over fire safety with escalated into uncalled-for and unwelcome dominance behaviour from my supervisor. All attempts to deescalate were rebuffed, and now there is litigation from multiple plaintiffs, this person took out her sociopathic tendencies on many people. With a minimum of professional detachment or a HR department wi…

I wasn't denying the existence of antisocial people, I was decrying the public shaming of someone you've never met as a victim of child abuse, and now also as a sociopath, based on only a small thing they wrote on the internet.

I assure you, I've met many people who treat their interviewees worse who are not sociopaths.

Re: Steve Ballmer's incorrect binary search interview question

#243

Post by alain94040 »

gcanyon wrote: post #83
kibwen wrote: post #22

Earlier quoted context omitted.

The ultimate conclusion of which is likely that both parties will decay to picking the secret value/first guess randomly (although I'm not sure if the optimal distribution is perfectly flat?), which is also something that we can model.

Seems like the distribution definitely won’t be flat since the guesser can randomly choose any of the numbers from 37 to 64 as a first guess without losing anything on the large side, so Ballmer starting with any of those increases his chance of having to pay out the $5. Likewise for other numbers there are nuances to what can be guessed.

But if you assume that the opponent knows that they shouldn't pick between 37-64, doesn't that change your odds?

The game theory here is similar to another quiz "Guess 1/3 of the average".

You are really trying to guess how deep the other has thought about the problem, so you can tell which strategy they settled on, and then you adapt your strategy based on that. Of course, it's a loop.

Re: Steve Ballmer's incorrect binary search interview question

#244

Post by kamaal »

carlmr wrote: post #226
kamaal wrote: post #217

I once had a colleague who had a favourite interview question, it had something to do with graph data structure and would always ask the question, many times candidate would reply and get rejected, strangely enough after a while all those candidates who replied got rejected. So we all gathered around him to work through what questions he was asking. We got to this question, and working with him on this question for a…

>strangely enough after a while all those candidates who replied got rejected. That also seems like a bad interview strategy. Make a mistake and you're out? Did you have so many perfect people to hire that you could just sort out almost everybody?

Its the standard narrative at every place "We always hire the best". No body knows where the not-best people work at.

They have to pretend to like they are working on things so special and hard that only the absolutely best would cut it.

Re: Steve Ballmer's incorrect binary search interview question

#245

Post by ozim »

crazygringo wrote: post #194
extr wrote: post #146

Earlier quoted context omitted.

Yes, I have used questions like this before for junior roles and the notes for the interview were something like: - Asked/did not ask clarifying questions - Did/did not (or could not, on prompting) verbally walk through their reasoning - Could/could not articulate which assumptions they felt were most important/why Nothing about the actual content of the question itself, or if your answer was approximately correct (I…

Yeah, I think there's a possible pitfall with using this as an interview technique though. When you're in a real situation with a customer or user, you ask tons of questions. You use a lot of common sense to figure out what they really want, what's actually important, etc. But often times these interview questions -- like how many vacuum cleaners in a city -- don't need any further questions asked. The idea that you'…

Well cannot agree really.

Assumption is mother of all fuckups.

I’ve seen customers wanting X and assuming that you should know that X comes with A and B because everyone in their business knows that. But you implement only X with A because you made your own assumptions and did not ask. So you missed the deadline and customer that’s it.

Re: Steve Ballmer's incorrect binary search interview question

#246

Post by patal »

whimsicalism wrote: post #102
layer8 wrote: post #100

Earlier quoted context omitted.

If Ballmer is being adversarial, he won’t pick the number at the start, and always win. Of course you can set up the game such that Ballmer has to commit on a number at the start of the game (by sealing it in an envelope or whatever), but that wasn’t specified.

they’re being adversarial within the framed rules of the game, not breaking the rules of the game?

Without writing the number down, it's up to Ballmer to decide that aspect, because you cannot look into his brain, or prove that he didn't commit to a prior number. Therefore, it's fair game.

Re: Steve Ballmer's incorrect binary search interview question

#247

Post by delian66 »

HarryHirsch wrote: post #237
rpdillon wrote: post #121

Earlier quoted context omitted.

I strongly agree with the sibling comment that this is a perfectly valid interview question. One of the biggest red flags in an interview is if I ask a question and the person doesn't know how to say 'I don't know', because it suggests there's a big risk that if I assign them a task in their day-to-day work, they won't tell me if they feel unprepared to tackle it. That's a far bigger issue than not knowing that trace…

The problem with "I don't know" is that it's really not culturally appropiate to say! Americans are supposed to be rugged, resourceful individualists and asking for help is frowned on because it shows weakness. Can't do that in an interview!

"I do not know" is not asking for help. It is a statement of fact.

Re: Steve Ballmer's incorrect binary search interview question

#248

Post by xandrius »

IshKebab wrote: post #34
pbiggar wrote: post #29

"Should you accept to play this game?" Absolutely yes. I like games. The purpose of games is to have fun. This seems like a fun game for like the first $20, a sum I can afford to play a fun game for 10 minutes. Then at the end, I get to say "I once lost $20 to Steve Balmer playing binary search", which is a fun sentence I can dine out on, and is worth more than $20 to me. I feel like perhaps this is why MS under Balm…

I don't know why you'd make this comment... I find it hard to believe you're actually stupid enough to not understand the implicit "(i.e. is your expected profit greater than 0)". If you answered like this in an interview I would definitely not give you the job. I did actually interview someone once who was like this - "How would you do this?" "Well you shouldn't do it. I think you should do this other thing.". He di…

I would be glad not to given a job then, if that's how you react to someone taking the quiz and giving it its own twist.

It's like interviewers don't understand the power dynamics going on during an interview: for the interviewer, this is just their job. Nothing will change for them whether they pass the candidate or not. This could be their 100th interview. On the other hand the interviewee is not paid to be there, they could be doing something else and they are stressed as who knows what kind of egocentric asshole might be interviewing them for a job they want.

If I get a candidate who can make a fun and clear headed remark in such a tense situation, I would read that as them being comfortable with problems and with stress. I would move forward and ask further questions to see their thought process but rejecting someone out of a single question is ludicrous.

Re: Steve Ballmer's incorrect binary search interview question

#249

Post by gcanyon »

alain94040 wrote: post #243
gcanyon wrote: post #83

Earlier quoted context omitted.

Seems like the distribution definitely won’t be flat since the guesser can randomly choose any of the numbers from 37 to 64 as a first guess without losing anything on the large side, so Ballmer starting with any of those increases his chance of having to pay out the $5. Likewise for other numbers there are nuances to what can be guessed.

But if you assume that the opponent knows that they shouldn't pick between 37-64, doesn't that change your odds? The game theory here is similar to another quiz "Guess 1/3 of the average". You are really trying to guess how deep the other has thought about the problem, so you can tell which strategy they settled on, and then you adapt your strategy based on that. Of course, it's a loop.

Yep, definitely not just what I said. I was saying that guaranteed it won't work out to an even distribution, not what the distribution would be.

Re: Steve Ballmer's incorrect binary search interview question

#250

Post by gukoff »

kibwen wrote: post #10

The article implies that the interviewee assumes that the number is being chosen randomly, when Ballmer could actually be choosing adversarially. However, if the interviewee assumes that Ballmer is being adversarial, then you can pick a different value as your initial guess, which causes the probabilities to shift. Even the OP assumes that the interviewee will start guessing with 50, but, because of the way binary se…

Yes, you can counter the adversarial choices and win at least 7 cents per game :)

https://gukov.dev/puzzles/math/2024/09/05/steve-ballmer-was-...

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