In this article, I’m going to help you whiz through those dastardly technical interview questions. Ever wonder why manholes are round? Read on.
Let’s start with an easy one. This one is called “The Rope Bridge“.
Four people need to cross a rickety rope bridge to get back to their camp at night. Unfortunately, they only have one flashlight and it only has enough light left for seventeen minutes. The bridge is too dangerous to cross without a flashlight, and it’s only strong enough to support two people at any given time.
Each of the campers walks at a different speed. One can cross the bridge in 1 minute, another in 2 minutes, the third in 5 minutes, and the slow poke takes 10 minutes to cross. How do the campers make it across in 17 minutes?
Solution: Who gives a shit? Who asks retarded questions like this?
This one is called “Wanna Play?” (hint: No!):
i offer to play a card game with you using a normal deck of 52 cards. the rules of the game are some fucking arbitrary bullshit that make this bullshit mental masturbation way harder than it needs to be. if you can’t figure it out in 45 seconds, i’ll assume you can’t produce code and work on a team, regardless of any free software projects you may have participated in (in fact i couldn’t look at open source code you’ve written if i wanted to, i’d get fired), regardless of any nice code samples you have to show me, regardless of how quickly you can pick up new things, and so on.
Solution: Are you getting the point? Jesus christ, no fucking wonder companies who use these kind of questions can’t ship anything.
At least in the case of Microsoft, from listening to one guy who’s worked there, they ask these questions to see how you think. It’s kind of a “psych” test. They’re not necessarily looking for you to produce the one correct answer. They want to see how you work on problems. If you give up, or scratch your head and take forever to solve it, or ask for help, that tells them something about you that may be desirable or undesirable as a team member.
I didn’t know this for a long time. When I used to get asked questions like this, I fell back into the mindset of trying to solve a word problem in school. I assumed I was supposed to answer it all by myself, and come up with the one correct answer. The thing is, even though it may not seem like it, these sorts of questions can be treated as open-ended. Even though the interviewer spells out the problem, there might be other factors, like your own judgement, you can introduce into it. They may even be looking for that. That’s the thing. You never know what they’re looking for. The truth is they’re probably just “poking” you to see what you’ll do.
I agree. It really only tests one aspect of you that would be desirable/undesirable for the job. I think a good example of what an employer could add would be if they brought in a laptop with wi-fi access and then asked you about something you were unfamiliar with, to see how fast you could a) find the information online, and b) how fast you could assimilate and use it.
Comment by Mark Miller — July 9, 2007 @ 7:34 pm |
I probably shouldn’t rant too much about hiring practices because I’ve never hired anyone, but how does working through a problem out loud like that reveal about how you think? That’s what I never understood.
What these things favor is people who spend their spare time cramming on tech interview questions rather than writing code, getting laid, watching TV, sleeping, exercising, or whatever else. The way kids prepare for math olympiads is not to work through any old random math book – they work through math olympiad preparation books that have problems similar to the ones that get asked at olympiads.
I think it optimizes for people who know how to prepare for and do well on tests rather than people who can be productive members of teams that make good software.
Comment by Warren Henning — July 9, 2007 @ 7:43 pm |
I can cite a couple examples. The one about “Why is a manhole cover round?” is kind of a classic Microsoft question. There are any number of answers you could give for it. You could say, “Because it’s easy to roll”, or, “Because the sewer pipes are made of a standard size of pipe, and a round cover fits them.” Something like that.
I don’t know if your “get across the bridge” problem is genuine or one you made up. It seems like a Kobayashi Maru test (no-win situation), but what I’d take a stab at with it is to say, “I’d take the 1-minute guy, send him across with each of the other guys, giving the 1-minute guy the flashlight. Since the 1-minute guy is faster, I figure he knows more about the bridge, and maybe can see better at night. He’ll guide the slower people across to help them *go faster*. All I need is for two of the slower people to cross 1 minute faster (since 1-minute guy will have to come back across to guide the next guy with the flashlight). I’m going to take the bet/risk that 1-minute guy can do that.”
When I looked at that problem, one possibility I saw was that it was a management question, testing your ability to size people up and make a strategic decision that has the best chance of success (though not guaranteed). I looked at the times for the different people, thought for a bit, and one possibility I saw was, “Well, each of those times is each person crossing on their own. What if a faster person was travelling with each of them? Maybe they’d go faster.”
Comment by Mark Miller — July 11, 2007 @ 7:42 pm |
There is a “guaranteed” solution to the problem, actually; and if you consider what is being measured as problem-solving skills rather than programming skills, it’s quite reasonable to ask such questions. (And the answer you gave is a good one in that aspect, I would think.)
Comment by Trevel — July 13, 2007 @ 5:42 am |
an answer to the first puzzle is:
1 minute person and 2 minute person cross, 2 minutes
1 minute person comes back, 1 minute
10 minute person and 5 minute person cross, 10 minutes
2 minute person comes back, 2 minutes
1 minute person and 2 minute person cross, 2 minutes
total 17 minutes
in response to #4: it’s debatable whether this kind of question is really about “problem-solving” (however one might define that). if you want to test for “problem-solving skills” there are plenty of other good questions to use, ones that do not rely so heavily on tricks and that are more open-ended.
Comment by Kevin Lin — July 13, 2007 @ 7:16 pm |