Hacker News Reader

Comment by Luc | Hacker News Reader

> I've found that usually once I get asked one of these, that's the end of the interview. Why? Because I epitomize "think outside the box". You see, there are a number of different bus styles [...]

That's IMHO the wrong approach. Everyone who's thought two minutes about this problem realizes these issues. None of these are a show-stopper to making a reasonable estimate. It would be completely acceptable for you to say 'Okay, I'll assume a sort of schoolbus like in the Simpsons, let's say 12 rows of seats, we'll need about 2m of vertical space plus some extra for when the driver goes over a speedbump so tall people don't hit their head', etc. The point is whether you can make a quick estimate, so that when in a real work situation you are asked to do something tricky, you can work out whether it's feasible or not.

View on HN

How do you know that it's OK to make assumptions like that? How do you know that a quick estimate is acceptable? Is this level of accuracy acceptable? How do you know?

I can't get the point of this.

The interviewer wants to know how many golfballs fit on the bus, but he doesn't even know what kind of bus? He hasn't decided what things are on the bus, and how many of them, and whether there is a driver, and what kind of track he's going to be driving the bus on? And he probably doesn't know why the golfballs are being put on a bus at all? And he doesn't care as to what kind of accuracy this estimate is being made, as long as it just seems I've gone through some kind of motions?

This is ludicrous. It doesn't resemble any real-world task.

Yes it does!

'We have an idea for a game where you walk around a real-looking representation of London, with realistic traffic and people on the side walk. We'd like to have this on the iPhone, PS Vita and Nintendo 3DS. We want you to write the engine for it.'

So, what do you do, start developing and hope for the best?

The fact that it's balls in a bus and not polygons on a screen is not a negative. It makes clear that the point is not to test your knowledge of the RAM of each platform, the point is to see if you can reason while facing unknowns.

> I can't get the point of this. The interviewer wants to know how many golfballs fit on the bus [...]

No, no, no. The point is to see if you give up (a large proportion do), or if you make bad assumptions (e.g. hand-wavy 'Lets say there's 1000 golf balls in a cubic meter').

The polygons onscreen question is a far better one, as it gives me a clue about the reason for asking, the kind of assumptions I can make, and the level of accuracy needed. The golf balls on bus example does not.

Really? Because the times I've tried to "seriously" answer such questions it became apparent the person asking was looking for "THE" answer. In fact I was halfway into the effect of having seat belts included when the interviewer started gently feeding me "the" answer they were looking for. Why? Because they felt that there really was a "right" answer that folks could agree upon. Not surprisingly, said company folded two years later as I gather their client didn't agree...

Ah, in that case, you're quite right to walk away! It's just meant to see if someone can 'put their arms around a problem', a rough way of weeding out people who can't make a move until they have every answer, a blunt tool.

Sounds like you used it appropriately as a blunt tool to weed out the company :)

Reply on news.ycombinator.com