Read an interesting book How Would You Move Mount Fuji. The author does a little critique of the modern approach of puzzle interviews. His take-away – since an employer can legally no longer ask questions about age/gender/orientation/etc – we have moved to a new realm of interviewing. This method of interviewing attempts to ascertain the raw ability and behavior of the candidate devoid of these contexts. This is both for good and ill – as it can have a very dehumanizing effect. Interestingly enough, while this method of interviewing is still popular (and was the RAGE in the late 90’s early 2000’s) there have been more recent articles written about the problems of this style and possibly better ways of hiring.
For instance, Atari founder Nolan Bushnell says this method would likely not find the next Steve Jobs – and that he would not likely be hired by anyone today using similar methods. For creative jobs, he believes in finding the person’s passion is more important. Others have suggested that we actually get more narrow and hire by their knowledge of an important algorithm a company needs vs more general principles.
Either way, the fun part for me were the questions themselves. There was a list of Google interview puzzles that I liked too. Here’s a collection of some of the more interesting ones in his book, and from other sources. I find they break down into three categories – Fermi problems, hypothetical problem solving, and deducible problems:
Deducible problems: These are designed to see how good your raw deductive skills are:
- A country that only wants boys, every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?
- How many times in a day do a clock’s hands overlap?
- Explain the meaning and relevance of the term ‘dead beef’ as it relates to programming/debugging.
- You need to check that your friend, Bob, has your correct phone number but you cannot ask him directly. You must write the question on a card which and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure Bob can encode the message so that Eve cannot read your phone number?
- How many places on the earth can you walk 1 mile north, 1 mile west, and 1 mile south and end up at the same place? (hint, its far more than just 1 place)
Problem solving: These are designed to see how you would attack a problem and your thought process:
- Design an evacuation plan for San Francisco
- You’re the captain of a pirate ship and your crew gets to vote on how the gold is divided up. If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?
- You have eight balls all of the same size 7 of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two weighings?
- You are given 2 identical eggs. You have access to a 100-story building. The eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor. You need to figure out the highest floor of a 100-story building an egg can be dropped without breaking. The question is how many drops you need to make. You are allowed to break 2 eggs in the process.