Earlier this month, we posted “15 Google Interview Questions That Will Make You Feel Stupid“, their answers and then 15 more questions. Three million pageviews later, here are…

Answers To 15 More Google Interview Questions That Will Make You Feel Stupid

Question: Every man in a village of 100 married couples has cheated on his wife. Every wife in the village instantly knows when a man other than her husband has cheated, but does not know when her own husband has. The village has a law that does not allow for adultery. Any wife who can prove that her husband is unfaithful must kill him that very day. The women of the village would never disobey this law. One day, the queen of the village visits and announces that at least one husband has been unfaithful. What happens?

Answer from reader Olivier Coudert: The cheating husband problem is a classic recursion pb. Once all the wives know there is at least one cheating husband, we can understand the process recursively. Let’s assume that there is only one cheating husband. Then his wife doesn’t see anybody cheating, so she knows he cheats, and she will kill him that very day. If there are two cheating husband, their wives know of one cheating husband, and must wait one day before concluding that their own husbands cheat (since no husband got killed the day of the announcement). So with 100 cheating husbands, all life is good until 99 days later, when the 100 wives kill their unfaithful husbands all on the same day. Job: Product Manager. Photo: symmetry_mind

Question:If the probability of observing a car in 30 minutes on a highway is 0.95, what is the probability of observing a car in 10 minutes (assuming constant default probability)?

Reader ru offers this answer: The trick here is that .95 is the probability for 1 or more cars, not the probability of seeing just one car. The probability of NO cars in 30 minutes is 0.05, so the probability of no cars in 10 minutes is the cube root of that, so the probability of seeing a car in 10 minutes is one minus that or ~63 per cent Job: Product Manager

Question: Four people need to cross a rickety rope bridge to get back to their camp at night. Unfortunately, they only have one torch and it only has enough light left for 17 minutes. The bridge is too dangerous to cross without a torch, 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 one minute, another in two minutes, the third in five minutes, and the slow poke takes 10 minutes to cross. How do the campers make it across in 17 minutes?

Answer from an anonymous reader: One and two across (two minutes); one goes back (three minutes); five and 10 go across (13 minutes); two goes back (15 minutes); one and two cross (17 minutes) — and everyone’s safe and sound. Job: Product Manager. Photo: Jule_Berlin

Question: You are at a party with a friend and 10 people are present including you and the friend. Your friend makes you a wager that for every person you find that has the same birthday as you, you get $1; for every person he finds that does not have the same birthday as you, he gets $2. would you accept the wager?

Answer: Ignoring seasonal upticks in births, there’s about 1/365 probability that any other person has the same birthday as you and 364/365 chance that any other random person does not. Do not take this bet. Job: Product Manager

Question: If you look at a clock and the time is 3.15, what is the angle between the hour and the minute hands? (The answer to this is not zero!)

Answer from reader Matt Beauchamp: 7.5 degrees. Every minute on the clock represents 6 degrees (360 degrees/60 minutes). Every hour, the hour hand moves from one number to the next (in this case, it is moving from 3 to 4) which represents 30 degrees. Since it is exactly 1/4 past the hour, the hour hand is 1/4 of the way into its 30-degree trip or 1/4 or 30 degrees… which is 7.5 degrees. Job: Product Manager

Question: What is the probability of breaking a stick into three pieces and forming a triangle?

Since this question doesn’t say the sticks must intersect at their tips to form the triangle, the answer has to be 100 per cent. Any three sticks of any size can make a triangle. Job: Product Manager. Photo: markhillary

Question: There’s a latency problem in South Africa. Diagnose it.

This is obviously an extremely vague question, and there isn’t really one correct answer. A good answer is one in which the interviewee demonstrates familiarity with the term “latency” and enough imagination to come up with an interesting problem with an interesting solution. Job: Product Manager Photo: warrenski

Question: How many lines can be drawn in a 2D plane such that they are equidistant from three non-collinear points?

Answer from reader Denis: Three. Take any two of the points. Draw a line that is parallel to the line segment made by those two points and halfway between that line segment and the third point. Repeat for every combination of two points. Job: Software Engineer. Photo: Caveman 92223

Question: What’s 2 to the power of 64?

1.84467441 × 1019 This is a pretty easy answer to figure out when you’re not sitting in an interview with no calculator around. Job: Software Engineer.

Question: Imagine you have a closet full of shirts. It’s very hard to find a shirt. So what can you do to organise your shirts for easy retrieval?

There’s no one answer to this. The interviewer wants to test the interviewee’s imagination and creativity with problem solving. We feel like reader “Dude” might impress a Google interview with this answer: Organise them according to types of clothes like a HASH and then organise each type into a 2-3-4-Tree or RedBlack Tree. Job: Software Engineer. Photo: Brymo

Question: You are given a game of Noughts and Crosses. You have to write a function in which you pass the whole game and name of a player. The function will return whether the player has won the game or not. First you to decide which data structure you will use for the game. You need to tell the algorithm first and then need to write the code. Note: Some position may be blank in the game, so your data structure should consider this condition also.

Answer from reader Dude: The data structure that is required is a two-character dimensional array. Call the function to check the six conditions if there are any winners, the sixth condition is to see if there are any more spaces left. If there is a winner the characters X or O are associated with the players, in this case you need a flag. If there is a winner return the value to the calling function to end the game. If not the run the game. Job: Software Engineer Photo: frozenchipmunk

Question: How long it would take to sort one trillion numbers? Come up with a good estimate.

Here’s another question without one answer. The idea is to test the interviewee’s creativity. We like the simple answer two readers came up with: Merge Sort for sorting. O(1,000,000,000,000 Log 1,000,000,000,000) — Average Case Scenario; O(1,000,000,000,000 Log 1,000,000,000,000) — Worst Case Scenario. I’d guess you can do one billion operations per second, thus 3000 seconds. Job: Software Engineer

Question: Design an algorithm to play a game of Frogger and then code the solution.

The object of the game is to direct a frog to avoid cars while crossing a busy road. You may represent a road lane via an array. Generalise the solution for an N-lane road. Here’s the only answer we found for this one, from site Glassdoor.com: “One approach is to write a recursive algorithm that determines when to ‘wait’ or to ‘jump’ to the next lane, depending if there is an approaching obstacle in the next lane.” Job: Software Engineer

Question: How many resumes does Google receive each year for software engineering?

This is another question that’s about testing the job candidate’s ability to frame the problem in a simple way and then creatively solve it. Our answer: A candiate for Quantitative Compensation Analyst should know that Google hired about 3400 people in 2008. Figure 75 per cent (or 2550) of those hired were engineers and that, like Harvard, Google only accepted 3 per cent of those who applied. 2550 is 3 per cent of 85,000. Job: Quantitative Compensation Analyst

Question: You are given a list of numbers. When you reach the end of the list you will come back to the beginning of the list (a circular list). Write the most efficient algorithm to find the minimum number in this list. Find any given number in the list. The numbers in the list are always increasing but you don’t know where the circular list begins, ie: 38, 40, 55, 89, 6, 13, 20, 23, 36.

Here’s our favourite answer from reader “dude”: Create temporary pointers and start from the root. (Most of the time circular lists have front and back pointers.) Check if front is larger or if back is larger. If front is larger then you know you are at the end of the list and at the front of the list. If front is larger then traverse the opposite direction and compare numbers. If there is no root or a pointer pointing to any part of the list then your data is lost in memory. Job: Quantitative Compensation Analyst

The first person account over at Business Insider is an interesting one, because it shows that everyone at Google is subject to some high standards. One sample question is, “How much money you think Google makes daily from Gmail ads?” To which she blurted out the answer, “$70,000″ before quickly asking if they could ignore it while she figures out a better one.

Of course there are caveats to her story: She should have prepared more, she’s kinda naive about the type of questions they’re asking and maybe she’s just not really right for the Google culture. Still, it’s something worth checking out just for curiosity’s sake. [Business Insider]

Specter, who covers the science beat for The New Yorker, is pissed off. Forces on both the left and right have been coming down on good clean science like never before. Yes, this “denialism”, as he calls it, comes from both sides. People on the left might think of it as Bush-flavoured Intelligent Design agendas and bans on stem-cell research, while those on the right would recognise liberal whining about vaccinations and genetically modified food. It’s all of these factions, and plenty more.

And in his new book, Denialism: How Irrational Thinking Hinders Scientific Progress, Harms the Planet, and Threatens Our Lives, Specter demonstrates that ignorance is death.

For our discussion — fitting the theme of This Cyborg Life — we singled out synthetic biology, a pursuit, as Specter describes it, that “by combining elements of engineering, chemistry, computer science and molecular biology, seeks nothing less than to assemble the biological tools necessary to redesign the living world”. Here’s an edited version of our discussion:

So we’re talking about, synthetic biology, the ability to take cells or small organisms and turn them into machines?

Yeah, that’s essentially where building machines, unbelievably complex ones, that will eventually be able to do whatever we want, out of cells and chemicals.

Yeah, so we just mix some chemicals in a pot and suddenly we’ve got a car manufacturer?

Well, it’s a little more complicated than that, but that’s the direction we’re moving in — you put some chemicals together and you get an organism, and then you get a more complex organism, and you get organisms that’ll do things, and you can get drugs or chemicals or plastics or fuel… These [scientists] are trying to take basic sugars, basic chemicals, and make it so they can digest carbon (which is kind of exciting though we’re not there yet) or just diesel fuels, plain fuel, that doesn’t emit any sort of greenhouse gasses. That has happened in small scales — we’re there. It’s just a question of scaling.

So why is this kind of low-level synthetic approach better doing than, say, the guys making fuel from algae?

I think the hope is that this will be cheaper and more stable. I don’t know that it’s better. I’m sort of agnostic on that, I think you’d rather have a lot of different approaches that are kind of greenhouse-gas neutral. And whatever works, you’ll use. And you know we’re not gonna have one source of energy, we’re gonna have a bunch. We’re gonna have wind, we’re gonna have solar, we’re gonna have chemicals.

When we look at the malaria drug [one of the first products that can be manufactured through synthetic biology — and a project funded by the Gates Foundation], they are going to be able to make all the drug that is needed in the world in a couple of vats. One of the reasons that’s exciting is because it’s a stable, easy way to regulate the manufacturing, to make sure that it’s done properly. We have a big problem with malaria medicine because it’s misused, it’s taken the wrong way, it’s counterfeit — and this is a way of regulating it. I think we’ll see that with energy sources too. It’ll be solid.

In the book, you refer to the opening of the Will Smith film I Am Legend, when doctors say they’ve harnessed the measles virus and turned it into a cancer killer, a mutant virus that eventually turns everybody into zombies. But two years after the movie comes out, real doctors from the Mayo clinic say that they’re using measles strains as a real cancer treatment, in real life.

The point I’m trying to make is, these things are a little scary. Anything that powerful has to have a downside. And we need to know what the downside is; we need to talk about the downside. And we need to acknowledge it exists and say to ourselves — and sometimes we won’t agree — but say to ourselves, “Gee, you know what, the potential benefits outweigh the risks.” Sometimes we won’t think that. But I do believe that lots of times, given the information, we would think that way.

We’re on the verge of creating our own viruses that go into the body — I mean, is that right? — they go into the body and they do something good rather than bad.

Yeah, but the thing is, that has a bad connotation but it ought not to. There’s a guy named Eckhard Wimmer who created a fake version of the polio virus, and lots of people screamed, because why would you do that? I even trashed him in an article once and I was wrong and so were those people. What he had been trying to do was to make synthetic vaccines. In order to make totally synthetic, rapidly reproducible vaccines, you need to understand the viruses. Wouldn’t it be great if, for H1N1, instead of growing tons of this stuff in eggs in Pennsylvania, we could just gear up instantly, making in factories all around this country, so that we could have millions of doses in two weeks? That’s not a pipe dream; that can happen.

Who says whether this kind of research happens or not? Who pounds the gavel?

If you live in America, it’d be some sort of democratic process. We need to have some sort of regulatory framework. Who approves a new drug? It isn’t just a pharmaceutical company that says, “Hey, I’ve gotta drug, let’s put it out there.” No, there are tons of hoops to jump through, and we need to have some hoops. And we need to make those hoops reasonable so that they’re not so ridiculous that no-one bothers to try to jump through them but not so easy that we’re endangering our citizens.

But the scientific progress will probably continue regardless of whether there’s a discussion or a regulatory framework?

I’ve never seen anything in the history of our planet where human progress has stopped. People have gotten in the way, people have slowed things down, but yeah it continues. People do the work. And so I think we kind of need to get on board and harness that work. Some people said, “we need to stop some things”, but I don’t think that can happen. I don’t think we can turn information back.

Right. In your book, you mention that Bill Joy’s argument was to just put a padlock on certain venues.

Yeah, and I understand why he said that, I just don’t think it’s realistic. I don’t think that’s the way the human animal is built or has ever acted.

The point I think that you make in the book is that, if American science infrastructure bans certain researches, it’s not gonna stop people who are outside America from doing the research, and maybe won’t stop people who we definitely don’t want to be doing this research.

It’s true. Look at the stem-cell ban. People went elsewhere to do it. It set us back, it set the world back. But it isn’t like it stopped. That’s a good thing, but it could be a bad thing. If we’re gonna do sort of high-end synthetic biology and be creating all sorts of exciting but theoretically scary things, let’s do it in this country. Let’s not have it done in some place with no regulatory system.

What’s the worst thing that could happen here?

You mean like in terms of?

I mean in terms of messing around with this particular biological technology.

Look, the worst thing that can happen when you mix genes around is you can let something loose that you can’t bring back that destroys, you know, fill in the blank. Humans? Animals? Life? That is the worst thing. That is the doomsday scenario and it… it can happen, these things can happen.

We have had agricultural biotechnology for 35 years and we’ve planted two billion acres. And people still talk about how it’s untried and untested. It isn’t untried. It isn’t untested. It doesn’t make people sick. It doesn’t mean there aren’t problems with it. But to go right to the idea that the worst thing will happen, it’s crazy. There’s always a worst case scenario. We don’t need to assume it. We need to think about it.

And then obviously the upside, this is the point of the book, the upside far outweighs the downside.

Yeah, you know, the worst case scenario is something goes awry and destroys the universe. OK, that’s the worst case scenario, and it’s a pretty remote likelihood.

Now, a pretty good likelihood is, if we continue living the way we live, my kid, who’s 16 years old, maybe she won’t live a whole life because people are dying of skin cancer like crazy in 50 years. This isn’t so long from now. We have really severe problems we need to address instantly. And those are the potential benefits of this research. We don’t talk about that very much. We need to do the work and find out and make our decisions and not decide beforehand that it makes no sense.

If this has piqued your interest, or if you’re just tired of people bitching about stem-cell research, genetically altered foods or the alleged evil that lurks in vaccinations, be sure to pick up Michael Specter’s amazing book Denialism: How Irrational Thinking Hinders Scientific Progress, Harms the Planet, and Threatens Our Lives, and meanwhile have a look at his most recent piece on synthetic biology in The New Yorker. Thanks Michael!

This week, Gizmodo is exploring the enhanced human future in a segment we call This Cyborg Life. It’s about what happens when we treat our body less as a sacred object and more as what it is: Nature’s ultimate machine.

The Wake Forest Institute for Regenerative Medicine, one of the world’s largest labs dedicated to regenerative medicine, is interested in repairing or replacing human tissue so the body can self-heal.

Interview With Dr. Atala

What can we do in organ growing/generation today?

Laboratory-grown organs and tissues are already benefiting patients today. For example, laboratory-grown bladders are being tested in children with spina bifida and adults with spinal cord injuries and will soon be tested in patients with bladder cancer. Tissue engineering technology has been used to repair narrowed urethras, the tube that empties urine from the body.

What will we be doing in five years?

We are currently working to engineer 22 different tissues and organs in the laboratory, including blood vessels, heart valves, bone, muscle, kidneys livers. Scientific progress isn’t always linear, so it’s impossible to predict how long it will take to reach our goals.

In 10?

In addition to tissue engineering, our lab and others are working toward cell therapies to benefit a variety of conditions, from diabetes to urinary incontinence and heart failure. There are many challenges to overcome — and the timeframe is impossible to predict — but we do see promise in these technologies.

In 20? (I know, totally nuts, but that’s what makes it so fun.)

I don’t know how long it will take, but I do foresee a future when organs will be available off-the-shelf, ready to “plug in” and replace injured or diseased organs. I believe we’ll have a boutique of technologies that will includes tissue engineering and cell therapies, and doctors will select the ideal treatment based on the patient’s needs.

[Lead image: A human bladder is engineered in the laboratory using a biodegradable, three-dimension scaffold that supports bladder cells while they multiply and develop. A technician is "seeding" cells on the scaffold. (Wake Forest Institute for Regenerative Medicine). For more information on these projects, go here.]

This week, Gizmodo is exploring the enhanced human future in a segment we call This Cyborg Life. It’s about what happens when we treat our body less as a sacred object and more as what it is: Nature’s ultimate machine.

Most of you may not have 16 minutes to spare on this and probably don’t care anyway, but I promised to post the full video, if only so you can understand the context of our five highlighted segments.

Watch it, share it, do what you like. And if you just want the short and sweet, here again are our five featured bits (shot and edited by Mike Short):

Steve Ballmer Exclusive Interview Series:
Part 1: Ballmer Talks Natal, Says Blu-ray Add-On for Xbox Coming
Part 2: Ballmer on the Smartphone Race: “It Doesn’t Matter What the Critics Say”
Part 3: Ballmer on Zune: Sometimes You Get It Right The Third Time?
Part 4: Ballmer on Those Crazy Ballmer YouTube Videos
Part 5: Ballmer Optimistic About Win 7, But Says Vista Is “Very Popular”

This is the one you’ve waited for, where I get Steve to talk about his animalistic YouTube persona. But how do you ask calm collected Steve about crazy sweaty Steve? Very carefully.

As you can see in the video, he’s not going to stop being himself, just because Bill Gates is officially out of the picture and the public finally sees him as the big man up top. Does that mean more YouTube excitement? If it does, you’ll surely see it here.

Stay tuned for more exciting Ballmer moments (and facial expressions), and then the full uncut interview video later today.

Steve Ballmer Exclusive Interview Series:
Part 1: Ballmer Talks Natal, Says Blu-ray Add-On for Xbox Coming
Part 2: Ballmer on the Smartphone Race: “It Doesn’t Matter What the Critics Say”
Part 3: Ballmer on Zune: Sometimes You Get It Right The Third Time?

And in the rare case you hadn’t seen the video I’m referring to:

Microsoft boss Steve Ballmer defended notorious products like Windows Vista and Windows Mobile throughout our interview, but when it came to Zune, he did seem to admit that Zune HD nailed what previous Zunes simply couldn’t.

When I asked if he gave an order to make Zune better, he replied:

Sometimes you get it the first time you cook the soup, sometimes it takes till the second time you cook the soup…You get better every time.

However you interpret that, it’s the closest Ballmer comes to saying that product improvement was needed, that it wasn’t just revision for the sake of the sales cycle.

Steve Ballmer Exclusive Interview Series:
Part 1: Ballmer Talks Natal, Says Blu-ray Add-On for Xbox Coming
Part 2: Ballmer on the Smartphone Race: “It Doesn’t Matter What the Critics Say”
Part 3: Ballmer on Zune: Sometimes You Get It Right The Third Time?

As someone who dabbles in music production on the side, I’ve long been a fan of producers who push technology: Herbie Hancock, Prince, Aphex Twin, and Richie Hawtin to name but a few. So RZA proudly admitting his geekdom isn’t a surprise to me — he’s a great producer. But my favourite quote from the video: “I rather raise nerds than raise gangsters.”

The interview was for his new autobiographical/philosophical book, The Tao of Wu, and took place at Manhattan’s USA Shaolin Temple. Fitting, because the interviewer dared RZA to show him some martial arts skills. The result below: [True/Slant via BoingBoing]

In the first segment of our exclusive Steve Ballmer interview series, the Microsoft CEO and I talk about Natal, the blurring of console generations, and the surprising fact that “you’ll be able to get” Blu-ray add-on drives for Xbox 360.

When I asked Ballmer about adding Blu-ray to the Xbox, he said:

Well I don’t know if we need to put Blu-ray in there — you’ll be able to get Blu-ray drives as accessories.

Though he says it with certitude, the timing of any kind of Blu-ray accessory is unclear. When I asked Xbox spokespeople about Ballmer’s revelation, they responded:

Our solution for HD quality video on an Xbox 360 is coming this fall with Zune Video and 1080p instant-on HD streaming. As far as our future plans are concerned, we’re not ready to comment.

Maybe something cooking for CES?

As you can see in our back-and-forth, Ballmer plays his cards close to the chest, but in my sit-down interview with him, he shared a lot. Prior to the Blu-ray business, Ballmer and I talked about Natal, and the excitement that Matt and Mark experienced when they stepped into the chamber back at E3. When I asked him if Natal was Microsoft’s attempt to do away with concept of game console generations (thereby prolonging the life of a given platform indefinitely), Ballmer smiled knowingly and said, “We’ll see.”

Stay tuned for more exciting Ballmer moments (and facial expressions) over the next day, and then the full uncut interview video on Friday.

In all seriousness, Dyson’s legacy is about more than a few home appliances — though they’re no doubt impressive. He’s a brilliant designer and inventor in an industry starved for brilliant designers and inventors; he’s got a clear enthusiasm for what he does, and he’s become a sort of evangelist for engineering and inventing; also he’s a nerd. I had, like, three minutes with the man, but managed to blurt out a couple of questions.

We started on tech:

Giz: PC or Mac?

Sir James: (Emphatically) Mac! Since 1984. I bought the first Macintosh.

Giz: What kind of phone do you carry?

Sir James: Well, I have a BlackBerry and an iPhone.

Giz: Are there any unlikely companies or designers that you see doing really interesting stuff right now?

Sir James: There’s my son, who does lights where he varies the angle of the light in quite an interesting manner.

Giz: So they’re not lasers?

Sir James: No, they’re regular lights. They’re floor lights where the shade goes up and down to create a wide or narrow beam. There are wall and ceiling lights which have barn doors as a shade; you get an amazing effect on the wall. I don’t know if nepotism is allowed on Gizmodo. [Ed. note: It is! So here's how they work:]
We also run a student competition around the world, and there are some really interesting ideas that come out of that.

Giz: You’re fond of removing requisite parts from things—bags from vacuums, blades from fans—is there any particular part in another device that you just want to get rid of?

Sir James: Well, I’m sure there will be, but I don’t think we should talk about it now. But yes, it is quite a nice approach to minimalism, removing things — well, removing things that cause problems; that’s the point.

Giz: Have you thought about directing your talents away from domestic inventions, and toward something more altruistic? Do you have any projects or dreams outside the world of Dyson?

Sir James: (Laughs) I’d like to do a better vacuum cleaner, but there’s all sorts of things I want to do. We’re very interested in encouraging people to get into design. In the West, we’re training far too few engineers and scientists. Schoolchildren love science and love technology, but somehow their parents, teachers and society tells them that other things are going to be far more interesting, so I’m on a bit of a mission to try and change that.

And as quickly as he stepped into my mic range, he stepped back out. Later, James!

You can read Mark’s review on Dyson’s $US300 bladeless Air Multiplier fan here, as well as the rest of our Dyson coverage.