I was discussing recently with friends that it would be amusing to create a computer science reference for parents.

So for those of you out there who know something about computers and babies, I offer a few definitions.

critical section

The urgent period between removing the old dirty diaper and securing the clean new one.

code review

A diaper fails the sniff test, and you request a clean-up.  Ideally this is done by the person who was holding the baby when the error occurred.

core dump

Self explanatory

debugging session

You lift the baby, sniff the diaper, but can’t make an obvious conclusion.  You start opening layers of clothing in search of additional evidence.

scope creep

You ask spouse to “hold” the baby, knowing full well that a diaper change is already needed.

turing machine

A device which formerly accepted tape as input, but is now gummed up with oatmeal.  “Turing complete” means “filled entirely” with oatmeal.

code re-use

Examine yesterday’s clothes for obvious signs of stains / barf / poop.  Continue using if they don’t look or smell too bad.

heap

An arrangement of toys, ideally in a storage bin.  Often these are scattered randomly around the house; we call this “fragmentation”.

thrashing

You cannot get out of the house because each child poops / barfs at a frequency greater than they can be cleaned up and prepped for departure.

port exhaustion

Juggling baby, bottle, barf cloth, iDevice, tissues, you finally run out of appendages available to hold anything.

child process

What you got.

sleep(unsigned int seconds)

This is formally deprecated, having been delegated to child processes.

encapsulation

You hired a baby sitter.

resource leak

Maladjusted diaper results in loss of … resources.

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Here is my part 2 follow up from Oddball Questions Part 1.

These are my responses to the Top 25 Oddball Interview Questions from Glassdoor, presented in Snappy Answers format.

Snappy Answers 13-25

13. “Name 5 uses of a stapler without staple pins.” – (EvaluServe)

Snappy answer: Entirely useless. See also: caffeine-free coffee and alcohol-free beer.

Alternatively (1) dental drill (2) geosynchronous satellite (3) pizza cutter (4) forklift (5) crampon.

14. “How much money did residents of Dallas/Ft. Worth spend on gasoline in 2008?” – (American Airlines)

Snappy answer: About $3.00 a gallon?

15. “How would you get an elephant into a refrigerator?” – (Horizon Group Properties)

Snappy answer: Cuisinart (The easy answer – this question is the subject of some amusing math responses)

16. “You have a bouquet of flowers. All but two are roses, all but two are daisies, and all but two are tulips. How many flowers do you have?” – (Epic Systems)

Snappy answer: None, I tossed them out after they wilted.

17. “How many planes are currently flying over Kansas?” – (Best Buy)

Snappy answer: Euclidean or Cartesian?

18. “How many different ways can you get water from a lake at the foot of a mountain, up to the top of the mountain?” – (Disney Parks & Resorts)

Snappy answer: Infinite number of ways. Isn’t that obvious?

19. “What is 37 times 37?” –(Jane Street Capital)

Snappy answer: BD1

20. “If you could be a superhero, what power would you possess?” – (Rain and Hail Insurance)

Snappy answer: The power to end senseless interviews in a single bound!

21. “If you were a Microsoft Office program, which one would you be?” –(Summit Racing Equipment)

Snappy answer: Notepad.

22. “Pepsi or Coke?” – (United Health Group)

Snappy answer: Yes please.

23. “Are you exhaling warm air?” – (Walker Marketing)

Snappy answer: Get your hand off my leg, you pervert.

24. “You’re in a row boat, which is in a large tank filled with water. You have an anchor on board, which you throw overboard (the chain is long enough so the anchor rests completely on the bottom of the tank). Does the water level in the tank rise or fall?” – (Tesla Motors)

Snappy answer: If the anchor is thrown far enough so it clears the side wall of the tank, the level will rise. If the anchor consists of a massive sponge larger than the tank, then the level will fall.

25. “How do you feel about those jokers at Congress?” – (Consolidated Electrical)

Snappy answer: They’re not nearly as funny as I am

One item I really enjoyed was Al Jaffee’s Snappy Answers to Stupid Questions, and those come to mind as I continue my thread on interview questions.

Oddball Questions

Glassdoor recently had an article titled Top 25 Oddball Interview Questions.

Oddball, indeed.  In reading them over, was sorely tempted to answer them with “snappy answers”.  Here are a few for your amusement.

The original questions from the article are in this color.  The snappy answers are basically what occurred to me when I first read the question.

Snappy Answers 1-12

1. “How many people are using Facebook in San Francisco at 2:30pm on a Friday?” – (Google)

Snappy answer: All of them.  It’s San Francisco.

2. “Just entertain me for five minutes, I’m not going to talk.” – (Acosta)

Snappy answer:

3. “If Germans were the tallest people in the world, how would you prove it?” – (Hewlett-Packard)

Snappy answer: Measure all instances of Germans pairwise against all other humans by transporting them all to Düsseldorf and placing them back-to-back in the Marktplatz . This means measuring all 81 million Germans against the other 7 billion inhabitants. This only requires worst case  67,000,000,000,000,000 comparisons and hence is computationally efficient. We can accomplish this in a few hours on a dual core Pentium, though it may require a little more time on an Apple ][ running iOS.  If all Germans are pairwise taller than all other humans, it is proven.

4. “What do you think of garden gnomes?” – (Trader Joe’s)

Snappy answer: White hat or black hat?

5. “Is your college GPA reflective of your potential?” – (Advisory Board)

Snappy answer: Not sure why they would be related.  To measure my potential, I recommend a voltmeter.

6. “Would Mahatma Gandhi have made a good software engineer?” –(Deloitte)

Snappy answer: Unlikely. This great man passed in 1948, only two years after the debut of ENIAC.  Though Turing complete, programming the ENIAC was pretty far removed from what we now call software engineering.

7. “If you could be #1 employee but have all your coworkers dislike you or you could be #15 employee and have all your coworkers like you, which would you choose?” – (ADP)

Snappy answer: If the company has fewer than 15 employees, I’d choose #1.

8. “How would you cure world hunger?” – (Amazon.com)

Snappy answer: First solve for global conflict; this generalizes to solve world hunger by side effect.

9. “Room, desk and car – which do you clean first?” – (Pinkberry)

Snappy answer: Work from home.

10. “Does life fascinate you?” – (Ernst & Young)

Snappy answer: Very much so! I particularly like the Gosper glider gun.

11. “Given 20 ‘destructible’ light bulbs (which breaks at certain height), and a building with 100 floors, how do you determine the height that the light bulb breaks?” – (QUALCOMM)

Snappy answer: Drop one from the 100th floor.  If it breaks, you have found a height at which it breaks.  If compact fluorescent, report to the EPA.

12. “Please spell ‘diverticulitis’.” – (EMSI Engineering)

Snappy answer: P-I-T-A

More soon.

One of them went bad on me recently.  The pedal was making crunching noises and wasn’t rotating properly – not good!  Apparently a ball bearing crumbled. 

Reading online reviews, it seems others have had this problem, too.

I decided to replace them with another pair of folding pedals.  I use the bike almost exclusively for commuting to work.  When folding the bike up for the train, I don’t normally need to fold the pedals.  But the folding pedals do come in handy on rare occasions when I put the bike in the trunk of my car. 

I chose a pair of MKS FD-7 pedals for the swap (pictured to the above right).  These are an upgrade both in terms of durability and grip.  The serrated edge prevents my tennis shoes from slipping much better than the rubber on the Suntour pedals.

These apparently come in black finish in addition to silver.  In retrospect, the chrome pedals make the bike look a little bit pimped-out.

A few years back, a colleague asked me to ponder a Wizards and Dwarves puzzle as a potential interview question.  A typical statement goes something like this:

A village of wizards is nearby a village of dwarves.  Once a year, the wizards visit the dwarves, and line up the dwarves in increasing order of height, so that each dwarf can only see the dwarves smaller than himself.

The wizards have white and black hats.  They place a white or black hat on the head of each dwarf (using a strategy of their choosing, perhaps even randomly).  Then starting at the back of the line (the tallest dwarf), they ask each what color hat he is wearing. 

Each dwarf who answers incorrectly is killed by the wizards.  The other dwarves can hear his answer, but do not know whether he was killed.

What strategy minimizes the number of dwarves killed?

Ok, I thought about it.

Pondering

Among many irritations I have for puzzle questions, the fiction is frequently distracting: 

Why villages?  Why wizards and dwarves?  Why in order of height?  What if they are all of the same height?  How can you kill a dwarf and not have his neighbor nearby hear it?

And my brain spins with other tangents:

Dwarves have high magic resistance and constitution – don’t they get a saving throw?  Toss in a few +5 battle axes and there would be a wizard slaughter!

Meh.

Wizards, Dwarves and Barometers

In the spirit of the barometer question, I formulated the following responses:

• Non-violent non-cooperation.  It is not stated that there is a penalty for non-cooperation.  In the spirit of Gandhi, the dwarves refuse to be sorted by height, do not line up, and will not wear hats.  Wizards are known weaklings and will be unable to forcefully move the dwarves into place.
• Scatter.  The dwarves split their village up into smaller villages, until each village consists of a single dwarf.  Each dwarf now has an equal chance of survival (this strategy, while fair, will be popular with the tall dwarves, but less so with the short ones).  The maximum number of dwarves killed will always be one.
• UN Convention on Genocide.  The dwarves are being unfairly singled out as a group for destruction.  Citing Resolution 260 (III), they appeal to the United Nations and await protracted discussion.
• Mini-guns.  Despite their diminutive size and desire peace, the dwarves obtain special weapons training, obtain mini-guns and when threatened, and whoop some major wizard ass.
• Mobile Phone.  First variant – dwarf uses a mobile phone to take a picture of his hat, revealing the color.  Second variant – dwarf snaps a photo of the dwarf in front of him and texts it to him.
• Low tech (no mobile phone required).  Dwarf turns around and asks the dwarf behind him the color of his hat.
• Vacation.  The wizards arrive once a year.  The dwarves arrange to be out of town on that day (ideally somewhere warm and sunny).
• Insubordination.  Each dwarf takes off his hat and reports its color.

And so on.

Conclusion

If you follow the intended script, you can find solutions in which no more than one dwarf is killed (the tallest has no knowledge of his hat color and his odds are essentially subject to chance).

But as shown above, one can simplify and further optimize the solution by exploiting ambiguities in the fiction.

And it’s a lot more entertaining.

A young fellow interviewing me asked a reasonable set of basic technical questions, had me code a few things on the white board (also reasonable), and so on.  The interview was pretty typical, and going well.

Near the end, he looked at me slightly askance, and said

“Ok, now I’m going to ask you a puzzle question.”

I may not have successfully resisted the temptation to roll my eyes as I responded

“Mmm, Ok.”

I’m not very fond of puzzle questions.

Barometers

He proceeded to ask

“Suppose you spot a building in the distance and want to estimate its height.  How would you do that?”

I chuckled and replied “That really reminds me of The Barometer Question.”  He blanched a bit and asked “What do you mean?” 

He hadn’t ever heard of it.

I proceeded to relate the story of the professor who asks a student how to measure the height of a building “with the aid of a barometer”.  The professor’s expectation is that student will provide an answer involving differential pressure from the base to the top. 

Instead, the student provides a list of unexpected, yet technically correct answers:

• Tie a string to the barometer and lower it from the top of the building until it touches the ground.  The length of string will be the same as the height of the building.
• Toss the barometer off the top of the building, time how long it takes to hit the ground, and solve for height.
• Offer the shiny new barometer to the building superintendent in trade for a peek at the blueprints.  The building height will be on the blueprints.

and so on.

“Wow, sounds like you’ve already heard of that one …”

said my dismayed interviewer.  (Indeed, though we eventually discussed the question and I provided him with a novel answer that satisfied him.)

Wizards and Monkeys

As puzzle questions go, this barometer variety isn’t too bad – at least it is amenable to multiple alternative, creative and valid solutions.

Puzzle questions which primarily involve a “gotcha” moment of perfect truth are in my mind essentially worthless for evaluating candidates.  In this category I have in mind classics such as Wizards and Dwarves, or the one on Monkeys and Switches.

These questions tend to result in a quick response if the candidate has heard them before, or a lot of fruitless struggling if they have not.  They generally don’t lend themselves well to systematic analysis nor extended discussion.

The puzzles are entertaining, for sure, but do you want to hire someone who can solve brain teasers, or do you want someone who can actually get work done?  Unless perhaps you run a company that authors brain teaser books …

In Joel Spolsky’s widely referenced article on Guerilla Interviewing, he too frowns on what he refers to as “Aha!” questions (the “gotcha” questions I refer to above), for similar reasons.

Out of the Box

Joel hedges somewhat more on what he calls “impossible” questions, like “How many piano tuners are there in Seattle?”  I’m a little more sympathetic here – I call those “out of the box” questions since you’re essentially looking for a candidate to approach a non-standard situation in a systematic way.

While I find those questions slightly more useful, they are less relevant for programmers than fundamental questions on algorithms, data structures, coding, design and architecture.  And in a 45-60 minute interview, I find I’m already pressed for time to cover those well.

As a result, if I’m ever interviewing you and ask you a puzzle question, it’s only because you’ve done very well.  It means I’d like to hire you, the interview is ahead of schedule, and I’m simply curious to see how you respond.

I’m secretly hoping you’ll roll your eyes, of course …

And if you ever ask me a puzzle question in an interview, I’m making a mental note to follow up (if hired) and speak to you about your interviewing techniques.

I’ve previously compared software estimation to variations in the time required to drive to work.

Dispatching delivery trucks is my mental model for comparison to changes in project direction.  This can help others to understand the impact when changes happen too frequently.

A Random Walk

Using an example from the Bay Area, suppose I have a delivery truck stationed in San Francisco.

I call up the driver and ask him to make a delivery in Sacramento.  For reference, Google tells me it takes an hour and a half or so to drive from San Francisco to Sacramento.

Suppose that, 30 minutes into the trip, I call my driver and tell him to make the delivery to San Jose instead.  He’d likely be near San Pablo, only a third of the way to Sacramento. 

The driver dutifully turns around, and starts the one hour trip to San Jose.

After another half an hour, I call him up and instruct him to drive to Tracy.  From somewhere near San Leandro (and short of reaching San Jose) he would start the one hour drive to Tracy.

And so on.

What Did You Accomplish Today?

After a day of this, I recall my driver back to the home office and inquire

“How did it go?  How many deliveries did you make today?”

Exasperated, my driver informs me that, in spite of driving hundreds of miles, he failed to complete a single delivery.

(As a manager, I then express shock and outrage, and we proceed to have a conversation in which perhaps I learn the error of my ways.)

Thrashing

In computer science thrashing refers to situations in which the resources of a computer are largely (or wholly) consumed by forms of overhead, with the result of severely reduced productive output.

The concept can apply to other activities, including projects.  Changes in direction (whether literal or figurative), can happen too frequently with the result that productivity is impacted (and in the worst case, entirely eliminated).

Make sure the driver has a chance to drop off the package.

Hidden Chronicles is a “hidden object” game in which you search for all the objects hidden within an illustration presented on the game screen (like the one to the right).  It also has mini-games and puzzles.

You can read more details in this VentureBeat article.

You can try Hidden Chronicles here

http://apps.facebook.com/hidden-chronicles/

Enjoy!

This recipe yields about 50 cookies.

Ingredients

• 1 cup butter, softened at room temperature
• 1/2 cup powdered sugar (plus more later to roll the cookies in, see directions below)
• 2 1/4 cup flour
• 1 teaspoon vanilla
• 3/4 cup chopped nuts (for example, small walnut pieces)

Directions

• Mix butter & powdered sugar well
• Mix in vanilla, flour and nuts
• Chill in refrigerator for several hours
• Shape into balls about 1 inch across (see picture to right)
• Bake at 400 degrees for about 11 minutes
• Roll in powdered sugar while warm.  For this I use a small baking pan filled with sugar (see picture to right)
• Once cool, roll again in powdered sugar

Once fully cool, they are ready to eat.

Enjoy!

Pecha Kucha

At NetApp we employed a similar format for “outrageous opinion” talks in engineering which I really enjoyed.  So I happily accepted a recent opportunity to perform a Pecha Kucha presentation at Zynga.

We used a slightly modified format (20 slides of 15 seconds each – 5 minutes total), but the principle is the same.  I chose to transform a longer presentation on scoping for 90% into the shortened format. 

For a technical presentation, that turned out to be a fun challenge. Here’s some things I learned from that experience.

Cadence

The timed format means that your presentation will be chugging along regularly, even if you are not.  If you haven’t mastered the cadence of your slides, the timing of your presentation will sound awkward to your audience.

To address this, you’ll need to know your slides end to end. 

That is, you have to have the sequence of your presentation in your head, so that for each slide you know which is coming next, to ensure a smooth transition.

You should be talking about the next slide in sequence before it shows up, otherwise your audience will wait through an uncomfortable silence.

Overall this is tricky to master.  I recommend several trial runs through your slide deck, with the last run ideally performed shortly prior to your presentation.

In other words, practice.  Watching some examples will help as well.

Visual Simplicity

Shoot for visual simplicity.  Uncomplicated pictures, graphs, smallish text snippets and callouts trump paragraphs of text.  Avoid big gobs of text and long lists of bullet items.

Swap graphs and clip art in place of text, whenever you can meaningfully replace the content.

With any presentation, strong reinforcing visuals are important.  In Pecha Kucha, they are golden.  The format is more friendly to purely visual presentations (design, art, architecture, …), and this fact needs to be leveraged for technical content as well.

5 Seconds

Your slides should take around 5 seconds for the average viewer to read and understand.  Any longer, and they won’t be able to listen to you, or might still be reading as you transition to the next slide.

If your presentation includes a slide with 20 bullet items and lots of text, you’ve got a problem.

Cheat: Repeat

If you’ve got a key point that requires more than the allotted time to present or reinforce, simply copy / paste the slide for a second repeated time slice.

In my talk, I used a slide in order to present a more complicated topic (for 15 seconds) and then repeated the slide with animated annotations to explain key points (for another 15 seconds).

Animate, Carefully

Animations can effective but require careful planning due to the compressed time format.

Powerpoint does a nice job by default of spacing the animations out over the time interval, if your presentation is on an auto timer. 

If your presentation cadence is really on the mark, the animations can appear just in time to support the points you’re discussing with the audience.

Wash, Rinse, Spin

To maximize impact, I arranged my talk in iambic pentameter.

Just kidding. I divided my talk into three sections

• Introduction, introduce the problem (5 slides)
• Concept and reinforcing content (14 slides)
• Conclusion (1 slide)

I limited the reinforcing content to two primary examples and one shorter example.  That was a little too complicated – if I did the talk again, I would limit to 1-2 examples. 

Limit the number of key concepts so the audience can absorb them in the short time allotted.

And good luck.