This is a fun book of puzzles of all types; mathematical, logical, algorithmic with food for thought on estimation, mind games and creativity. There is also lots of interview advice, when applying for a job. The advice is good not just for Google, but for many other companies as well.
I am straight away going to chapter six which has a gist: At Google, they believe in sharing ideas.
- It is okay to question interviewer if you don’t understand, ask for clarification.
- When asked to provide a solution, first define & framework the problem as you see it.
- If you don’t understand, ask for help for clarification.
- If you need to assume something verbally, check, it is a correct assumption.
- Describe how you want to tackle solving each part of the question.
- Always let your interviewer know what you are thinking as he will be interested in your process of thought as your solution. Also, if you are stuck, they may provide hints if they know what you are doing.
- Finally, listen, don’t miss a hint if your interview is trying to assist you!
The book
starts in a fairy-tale like narration. “If you are shrunk to a penny height
and thrown into a blender, what would you do to survive”? There are then several
solutions like, clinging to the central pivot, or hiding beneath the blades etc.
The author finally reserves an answer mathematically. “If you are shrunk to 1/n
of your usual size, muscle energy would be reduced to n3”, and thence comes the ‘idea’ that would be accepted by the Google.
What comes next, after 66? 10, 9, 60, 90, 70, 66,…
Ten, nine, sixty, Ninety, Seventy, Sixty-six, chose any number that has nine alphabets. At one point you would be required to go in terms of exponentials. It is then the birth of Google is explained. ‘Googol’ (1 followed by 100 zeros) was the predecessor to Google, and the word first came from Kasner. who wrote this in a book called “Mathematics and Imagination” that was later to be used up by the Google founders, after typing it mistakenly as Google, only to be sued by the family members of Kasner later.
The next chapter talks about the history of Human Resource which happens to be the crux of many a industry. The first ever question by HR was during World War 2, “Did you ever build a model plane that flew”? The Russian Sputnik company was first to use IQ when it tested candidates for its launch programme.
Some more questions from HR:
- “It is difficult to remember what you read, after many years, how do you address this”?
- “How do you describe a person from Mars”?
- “Using a 4-minute and 7-minute hourglass how would you measure 9 minutes”?
That IBM was the first to use ‘Software and Silicon Valley’ in their library of reserved words was a good information. Likewise, Stephen Wolfram was the person who introduced ‘Mathematica’ along with Feynman that solved for the first time the “Billboard problem” for first 10 digits of prime in consecutive digits of e.
The next chapter is on ‘Great Recession’ mainstreamed by bizarre interview questions.
Walmart
wanted to hire anyone with ‘pulse’ – ‘One size fits all’ was the expected ‘response’,
for their question “if anyone came without appropriate clothing, what would you
say”?
Here are
some sample questions:
- “What is your favourite internet product and how would you improve it”?
- “Estimate the amount of cash in your wallet”.
- “If you were a cartoon character, what would you be”?
- “How weird are you in a scale of 1 to 5”.
- “At 3:15 what is the angle between the minute and hour hands on analogue clock”?
- “How many integers between 1 and 1000 contain 3”?
The next chapter has details specific to Google. Human resource at google was known as People’s Operation where they would ask “When did you get your first computer”? Google founders had no privacy, and their cubicles are small enough to find out who was doing what. So, in one of their interviews, they had asked the candidates in a scale of 1 to 5, what they would choose - 1 is working alone, and 5 is working in team.
There would be at least five on-site interviews for any engineer who would be asked to develop an app they liked and for any question in between, the candidates’ opinion should likely be close to truth. No discussion among the candidates was allowed until report was submitted by all. Many have a rule of the thumb that they can’t go wrong, hiring a Stanford Ph.D. It would be a bias if the employer insisted that the degree our university do not matter and thus Google assigned optimum weight to everything. At Google, hiring is more bureaucracy than algorithm.
Trivia also forms part of the people at the helm of the interviews.
One
question that evoke awe was to explain the significance of ‘dead beef’. See if
you can get through the below paragraph.
Certain decimal numbers look like English words in strident, for example:
0993FF10
7229B236
223774290
DEADBEEF
‘Why is
a manhole round and not a square’?
Richard Feynman
got an interview at Microsoft, (apocryphal story) that why manhole covers were round
to which he replied, “covers are round by definition”, and that tautology was
most trivial answer considered.
Imagine a country where parents want to have a boy and they stop when a boy is born (else the births continue when girls are born). “What is the proportion of boys to girls in this country”? Google doesn’t want people who instinctively do things the hard way because they can – instead it expects simple solutions that is human element. The capacity to ignore what you have learnt is appreciated when it is not helpful.
A motive behind one of the interviews has been to find out what separates an entrepreneur from an engineer through the candidate. It should be the ability not to think like an engineer, when the entrepreneur has to ignore ideas and judge whether the end users will want or be able to use product.
How the
people (should) think was humorously narrated with a story:
A helicopter flying over Seattle malfunctioned and all its navigation panels failed. Due to fog and smog the pilot was not able to locate any identity of any location. The pilot then held out a sign in large letters asking -“where am I”, over a tall building that was partially visible. The people from the building replied in a similar manner- “you are in a helicopter”. The pilot, then safely landed in an airfield, and when the copilot asked how he was able to judge the airfield, the pilot replied that only people from Microsoft can give technically correct answer, (but a completely useless one), that helped him guess the building location.
Some more questions to think:
If you had a stack of pennies as tall as the Empire State building, could you fit them all in one room now. The answer is 'no' because a room of the size of 102 stories room doesn’t exist. But you can go on discussing it.
You’ve
got a clock with a second hand, how many times in a day, all the three-hands
overlap?
12:00:00
01:05:27
02:10:54
03:16:21 etc.
If you answer this rightly you might be asked to determine if any of these times is a three-hands overlap? (digitally)
Some logic puzzles like X +Y+ Z = N can be asked
Lateral thinking, puzzles like there are three women in swimsuits: Two are sad, and One is happy. The Sad One is smiling and happier and the Happier One is crying. Explain.
Test of
divergent thinking, like how would you compare the 'search engines' by taking out
an example?
Fermi
question like 'how many tennis balls can you fit in this room', warrants a casual
look around the room that should be around 1000 to 2000 cubic feet, and one
must remember the size of the ball to be between 2.5 and 2.7 inches, along.
Algorithmic
questions like “you have a wardrobe full of shirts, and it is hard to find what
you want to wear. How would you organise them for easy retrieval”? (You can organize it based on colour style,
stripes, checks, sleeves, less, etc. without suggesting extra cupboards!)
Explaining the sequence like what comes after
11
21
1211
111221
Well, you can literally read to find out the answer (like two 1 for the second line).
Art of visual solution is also on the anvil once you get through all answers.
Picture-based
questions like “a pizza must be cut into equal slices based on your consumption in 3 second and your friend's in 5 seconds".
*How many different ways can you paint a cube with three colours of Paint?
*How to estimate just about anything in 60 seconds or less like how much money Google makes daily on Gmail ads (roughly $70,000).
*Name a piece of technology you read about recently and tell your own creative execution for an ad for that product.
Fermi questions like these were more: Advantage: Fermi questions can help invent new ones easily.
(Because Fermi believed that anyone with PhD in physics should be able to estimate it)
*Estimate the number of taxis in New York.
*How many golf balls would fit in a stadium.
*How many seniors are there in four-year course in a University?
*Once Intel asked how many lines of C or C++ code the candidate has written for an app.
*How many toilet papers would it take to cover Greater London?
*How many ridges are there in the rim of US quarter?
*How many bottles of shampoo are produced in the world over a year?
*What is two power 64? The final chapter has a story to all the questions that follow.
You work in 100 story building and are given two identical eggs. You have to determine the highest floor from which an egg can be dropped without breaking. You are allowed to break both eggs in the process. How many drops would it take you to do it? Carl Mill of a School created this idea because he found that raw eggs usually do not break when dropped on grass, regardless of the height of the drop. A man then climbed a top 70-foot ladder and dropped 10 eggs into the grass out of which 7 survived and an RAF officer dropped 18 eggs from helicopter 150 feet above the ground and 15 eggs survived, which is 83%. So, for 100 floors, how would you estimate the floor from where egg would not break?
For this, you have to use the formula and try dropping from 10, 20, 30… floors gradually. If your second egg breaks at 58, that means the eggs-safe floor is 57. Google algorithm takes maximum number of drops needed to determine the correct floor. It is called as D and assuming from a single series D + (D -1) + (D -2) + … +3+2+1 equation can be written and from there algebra can be summoned for the solution.
This
section has another insightful question.
“How
would you estimate the weight of your head”?
Invoke
Archimedes principle. The amount of water displaced is equal the volume of the
part immersed. So, dip yourselves first and find out the water displaced. Then
dip your head only to find out the water displaced and subtract the latter from
former. But wait….. you have to define where the head ends and the body starts!
Many of the questions have no “correct” answers, but more accurately, the company has a “preferred” answer. And for inquiring minds you may be smart enough to work at Google.
A very interesting aspect of this book is that the last half of the book supplies not just the answers to all the puzzles, but detailed explanations as well. The style of the writing has a light touch and is often subtly humorous. The book is recommended for all those who like a diverse range of challenging puzzles.
The goal is to find out where the candidate run out of ideas.
