Saturday, January 28, 2006

** How would you move Mt Fuji? by William Poundstone

How would you move Mt Fuji? by William Poundstone

This book talks about the puzzle interview style that companies like Microsoft and Google use extensively. It contains many good puzzles that are quite thought provoking. In addition, it gives some generic advice to both interviewers and interviewees on how to get the best out of an interview.

Good interview questions:
1. Describe an instance in your life where you faced a problem and tackled it successfully
2. Describe when you had to work under a deadline and there wasn't enough time to fully complete the job.
But as an interviewer ask yourself this: Is there any conceivable answer to an interview question that would want to cause me to hire someone on that answer alone? Is there any possible answer that would cause me to want to hire them? p18

How to solve a puzzle question:
After brainstorming many possible ideas, the candidate should select the strongest idea. That is itself a test of critical judgement. Then the candidate should add any further details or elaborations needed to make the chosen idea a complete answer. It is important to conclude with all major gaps and contradictions resolved. p69

The challenge:
You look for the candidate to say something positively correct. Then you say 'Wait a minute' and argue with them that they are wrong. Weak candidates will give in. No hire. Strong candidates will find a way to persuade you. 'Perhaps I'm misunderstanding you.' But they will stand their ground. Hire. p88

Impossibly useful:
When an assumption leads to a proof that the puzzle is impossible to solve, then there is something wrong, either in the assumption or in the reasoning. p106

Obviously you're wrong:
Not sure where to start, see if you can figure out why the obvious solution is wrong. It not only fills dead air but also is an excellent way of understanding the problem. p125

Just do the opposite:
Assume the opposite of each assumption in turn. Does that lead you anywhere promising? You may find that one of the assumptions, when tossed out, leads to a solution. p 189

Here are some sample questions (where are the answers you ask? In your head I'm afraid. These are all solvable and have an answer.)

How would you weigh a jet plane w/o scales?

Which way should the key turn in a car door to unlock it?

If you're in a boat and toss out a suitcase will the water level rise or fall?

If you could remove any of the 50 states which would it be?

How many points are there on the globe where you can go 1 mile S, 1 mile E, 1 mile N, and you're back to the starting point?

How many times a day to a clock's hands overlap?

How do you cut a rectangular cake into 2 equal pieces, when it has a rectangular piece of any size or orientation already removed?

You have 8 balls. One is defective and weighs more. How do you tell, using a balance, which ball is defective in only 2 weighings?

You have 2 jars and 100 marbles. 50 are red and 50 blue. 1 jar will be chosen at random; then 1 marble will be withdrawn at random. How do you maximize the chance that a red marble will be chosen?

You have 3 qt and 5 qt buckets and lots of water. How can you measure exactly 4 qts?

You have a gold bar divided into 7 equal segments. Each segment represents the salary to an employee whom you must pay at the end of each day in gold. You are only allowed 2 cuts in the bar. How can you settle with the employee at the end of each day?

You have a bucket of jelly beans in 3 colors - red, green, blue. How many jelly beans must you take to be certain of getting 2 of the same color?

You have 3 picnic baskets filled with fruit. 1 has only apples, 1 only oranges, and the last has both. Each is labeled incorrectly. You can only pick the fruit from 1 basket. How can you determine what is in all 3 baskets?

I have a gun w/6 chambers and I place in 2 bullets that are in adjacent chambers. I point the gun at your head, and pull the trigger. You survive the 1st shot. I give you a choice since I will pull the trigger one more time. Should I spin the barrel or should I shoot again?

1 comment:

al fin said...

Very nice choice. It looks as if interviewers at elite corporations are using the "lateral thinking" approach to finding creative applicants. Poundstone should be congratulated for writing about this intriguing development.

Edward de Bono must be quite proud.