Data Interpretation for MBAs

Data interpretation is tested in both the GMAT and the GRE, and with good reason. It is critical that people working in STEM subjects, or going on to lead businesses be able to, at the very least, read and interpret data presented to them in various tables. Of course, more pressing for B-school students is the ability to be able to read and respond to case questions when studying for and completing various courses.

ChiPrime has built an interesting quiz that takes a step towards educating students in this regard. A free (Beta) version can be found here. The graphics in question are all from the Economist website and are from articles hosted by that magazine (copyright is intact - they do not copy or host any images on the site, just link to static images provided by the magazine itself). The Economist has excellent content, and perhaps the best data graphics and visualization of any magazine today. Reading articles from there also helps with reading comprehension and analytical thinking.

Quant/Programming Interview Question of the Day

These are simple warm up type questions meant to help you prep for interviews. They are each designed to be solved within 3-7 minutes, never more. Questions like these are routinely asked in job interviews where you have to demonstrate even the least bit of quantitative talent. I plan to post a new question every few days, with solutions before posting the next question. [While I try to provide sources for every question if I am aware of them, some of these were either asked by, or asked to, friends in interviews, so I cannot always definitively say which book they came from.] Good luck with your preparation and to landing the job of your dreams.

Edit: while I started posting questions with solutions, speaking with some candidates sometimes leads me to believe a lot of people tend to simply read the questions and solutions, and this does more harm than good. So going forward, I will still post questions as regularly as I can, but solutions only relatively infrequently.

Question for 2 Feb 2016:

A spherical shell is constructed such that the outer radius is equal to that of a circumscribing sphere for a cube of side S, and the inner radius is equal to the radius of the largest completely contained sphere in the same cube. If two regular tetrahedra (four equilateral triangle faces) T1 and T2 are constructed with corresponding parallel faces such that T1 is the largest one that can be contained in the outer bound of the spherical shell, and T2, the largest one that can be contained in the inner sphere, the volume enclosed between T1 and T2 is?

Question for 31 Jan 2016:
Derive tight lower and upper bounds for the sum sigma(i=1 to N) sqrt(i). i.e. sqrt(1)+sqrt(2)+...+sqrt(N). What about the sum sqrt(1/1)+sqrt(1/2)+sqrt(1/3)+...+sqrt(1/N)?

Question for 25 Jan 2016:
You enter a casino with $1,000,000. You repeatedly spin a "fair" roulette wheel wagering $1 each time on red or black. The wheel has 18 red slots, 18 black slots, and 2 white slots (marked 0 and 00). Each time you win, you get $1 plus the money you wagered, when you lose, you get back nothing. You leave happy if you make $100, you leave sad if you go broke (lose all $1,000,000). Which is more likely? Why?

Question for 20 Jan 2016:
There are N boys and N girls in a group of 2N people. Each boy has a list of the N girls ranked in decreasing order of preference. Each girl has a list ranking each of the N boys in her order of preference as well. Is there a way to ensure the creation of N pairs each with a boy and girl, such that no boy B has a better preferred girl X than the one he is paired with, where X also prefers him to her own boy B'? Explain an algorithm to achieve this.

Question for 18 Jan 2016:
You are given a 22 ounce glass and an 11 ounce glass. Can you measure out 4 ounces exactly using these two glasses? How, or why not?

Question for 17 Jan 2016:
Given an n x n square grid or chessboard (n=2^k), with any one square removed. Prove that it can always be completely tiled with L-shaped tiles each made up of three 1 x 1 square tiles.

Question for 16 Jan 2016:

Is it possible to arrange the dots on the faces of two dice such that they are completely different from each other, but yet, when they are rolled together, the probability of obtaining every "score" is the same with the modified pair of dice as it is with the original pair? [variant of the Sicherman Dice problem.]

Question for 16 Jan 2016:
In how many ways can you make change for a dollar (100 cents) using half-dollars (50 cents), quarters (25 cents), dimes (10 cents), and nickels (5 cents)? [Note: an elegant solution would use generating functions.]

Question for 14 Jan 2016:

Alice and Bob pick natural numbers p and q respectively completely at random uniformly from the range [2, inf). What is the probability that the larger of p or q is a multiple of the other?

Question for 6 Jan 2016:
The integers 1 through K, both inclusive, are arranged in a circle. You start at 1, then remove every mth integer from the circle, continuing with this operation till you are left with only one integer. Write a program that takes integers K and m, and returns the single integer you are left with at the end.


Question for 13 Dec 2015: [source: Quora]
Which is greater? The number of molecules of water in a glass, or the number of glasses of water in the ocean? You may choose any reasonable volume for a typical glass to perform your calculations.

Question for 20 Aug 2015: 
1. Write a program to lexicographically sort a list of integers without using strings. (5 mins)
     e.g. [1,11,121,1211,20,22,221,33] etc
2. Write a function that reverses the digits of an integer again without using strings. (3 mins)

Question for 30 Jun 2015: 
There are three cops (C) and three thieves (T) on the right bank of a river. A boat is also moored to the right bank at the start. They need to get to the left bank. The boat can carry at most two people at a time. Cops are only safe if there are equal in number, or outnumber the thieves. Write a computer program that gives a sequence of crossings that is feasible without the cops getting attacked. [You have 20 minutes to write, debug, and run the program.]

Question for 26 Jun 2015:
In how many ways can you sample 3 letters from the English alphabet without replacement, such that the three are in lexicographic order?

Question for 20 May 2015: 
Tommy goes completely unprepared for a 20 question multiple choice (4 options per question) quiz, and guesses randomly on each question without leaving any out. If each correct question is scored with 1 point and there is no negative marking, what is the probability that Tommy passes the test given the passing grade is 50% or more? What if there was a 1 point negative marking per incorrectly answered question as well?

Question for 7 Apr 2015: [credit: Quora]
Given a set of N people with birth dates and death dates (where applicable) - all between 1900 and 2000 inclusive - for people in this set, write a program that tells in which year the largest number of these N people were alive at the same time.

Question for 5 Apr 2015:
Given a sorted set of 1000 numbers, describe an efficient algorithm to generate a random permutation of this set - such that the random permutation has equal probability of being generated as any other random permutation that might be produced.

Question for 1 Apr 2015: 

1. Write equations using any mathematical symbols of your choice, and three of each number 1-9 to equal 6. E.g. write 9 equations using {1,1,1}, then {2,2,2}, ..., then {9,9,9}, but in each case, the equation must evaluate to 6.
2. Write equations using any mathematical symbols of your choice, and three 9s each time, such that the equations evaluate to numbers from 1-9 both inclusive.

Question for 25 Mar 2015: 

Prove that there are infinitely many prime numbers.

Question for 25 Mar 2015: 

1. Solve x = sqrt(2+sqrt(2+sqrt(2+ ... to infinity)
2. Write a Python program to evaluate the expression in (1) to prove your answer is correct.

Question for 15 Mar 2015: 

1. Solve x = 1+2/(1+2/(1+2/(1+2/.... to infinity)
2. Write a Python program to evaluate the expression in (1) to prove your answer is correct.

Question for 10 Mar 2015: 

1. Write a function that takes a string s of some number in base integer p, and returns its decimal representation. [getting this right on your first try is a prerequisite to advance to parts (2) and (3) below.]
2. Write a function F (x,y) that takes a decimal integer x and returns a string representation of x to base y. 
3. Write a function P (x) that takes a decimal integer x and returns a list of all the prime factors of x - repeating factors appear as many times as they occur.

Question for 4 Mar 2015: 
"Pi Compression". The transcendental number Pi has a never ending stream of non-repeating digits. So one might imagine that it contains absolutely any sequence of digits one might require, within its expansion, at some point in the sequence. Let us suppose you have a file p that has 1000 characters. Further suppose that you reduce this file into a sequence of digits from 0-9 using some transformation. Can you now compress file p by specifying the tuple (x,y) where x is the location in the infinite stream of digits in Pi where the sequence of digits for file p begins, and y is the length of p (whatever it takes to represent your 1000 characters in the numeric representation)? Would this work? Why or why not? [Answer will not be provided.]

Question for 4 Mar 2015: 
You are given an n x n grid of cells where each cell in an instance of the grid is randomly colored either black or white. A grid is called "open" if white cells are connected to form a path from the top of the grid to the bottom - two cells are "connected" if they share an edge. Else the grid is "closed". Explain what algorithm you will use to determine if a given grid is open or not. Implement it.
[Answer will not be provided.]

Question for 2 Mar 2015:  
Write a Python code snippet that asks for a three digit integer as input then returns the sum of its digits. You are given credit proportional to the number of exception cases you handle as you code this. [Answer will not be provided.]

Question for 28 Feb 2015:  (c) ChiPrime
A cube and a sphere can intersect in at most how many points?

Question for 27 Feb 2015:  (c) ChiPrime

Given 4 circles with centers at A, B, C and D each with radius R, which intersect each other in exactly one point P, what is the area of quadrilateral ABCD?

Solution: 
It should be obvious that A, B, C, and D cannot be coplanar. Imagine A and C are centers of two circles that are tangential to one another. B and D can then be circles that are similarly tangential to one another, with the same point of tangency P in any plane containing the tangent line of Circles A and C, or even any plane containing the line joining the centers of Circles A and C. In either configuration, the largest area of quadrilateral ABCD occurs when the two planes containing the circle centers are perpendicular to one another, so ABCD is a square with diagonals of length 2r or sides of length r*sqrt(2) for an area of 2r^2. The minimum area of ABCD would occur when two vertices in either plane are almost coincident with those in the other, giving an area that tends to 0.

Question for 10 Jan 2015:

There are 5 green and 45 red marbles in an urn. You pick blindfolded, ten marbles from the urn, without replacement. What is the probability that exactly 4 of the ten are green?

Solution:
This is an example of the hyper-geometric distribution. The problem cannot be modeled as a binomial distribution because the probability of a "success" event changes with each draw. Please see this wikipedia article for more details. The problem is also discussed and solved there. The answer is given by the expression (5C4)*(45C6)/(50C10) = 0.003964.

Question for 5 Jan 2015:

What is the probability that given a standard deck of 52 cards, a thorough random shuffling of the deck will produce an ordering where not a single card is in the same position (as it was before the shuffle)?

Solution:

This is again a problem of derangements. The ratio of the number of derangements to the total number of permutations approaches 1/e as n increases (beyond about 7 or so). Here we have a deck of 52 cards, so the probability of getting a derangement is about 1/e or about 37%. See this wikipedia article for details.
http://en.wikipedia.org/wiki/Derangement


Question for 2 Jan 2015: 

1. In a knock-out tournament, if there were 39 matches played in total, how many players participated in the tournament in total?
2. Using only three 9s and any mathematical symbols you like, write an expression that equals 20.
3. Using only three 4s and any mathematical symbols you like, write an expression that equals 100.
4. Using only five 0s, and any mathematical symbols you like, write an expression that equals 120.

Solution: 
I believe all the first three questions came from a book by Peter Winkler, but I don't have it, so I cannot be sure of the source. The last is one I ask(ed) in interviews.

1. If there are 39 matches played, there were 39 players that lost and one that won the championship, for a total of 40 players (remember, this is a knock-out tournament).
2. (9+9)/.9
3. (4*4!+4)
4. (0!+0!+0!+0!+0!)!

Question for 29 December 2014: 

In a class of 4 students, A, B, C and D, the professor has each student grade another student's homework (of course, no student can grade his own work). How many possible ways can papers be distributed to accomplish this?

Solution: 

The answer is equal to the number of derangements of 4 items, denoted by !4.
The (recurrence) formula for derangements !n=(n-1)(!(n-1)+!(n-2)). So for n=4, we get 9 as the answer, as shown on that wikipedia page.

Question for 3 December 2014: 

1. Given two strings S1 and S2, how would you determine if one was a permutation of the letters of another?
2. Given a string S1 with some repeating letters, how would you construct a permutation of S1 that is closest to a palindrome? [a palindrome is a string that reads the same back to front as it does front to back.]

(c) ChiPrime 2014

Solution: 

1. First compute the set of all letters in strings S1 and S2. If the intersection of these sets is equal to either of S1 or S2, next check if the number of occurrences of each element of the intersection set in each of S1 and S2 is the same.
2. First, split all characters in S1 into two lists - list X of all repeating letters, and list Y of all non-repeating letters. Now if X contains an odd number of any letter, move it out to Y, so X only has an even number of every letter. Now construct the palindrome string P with one letter each from letters in X (order does not matter here), making sure to end the string with the same letters in reverse order. Plop the set Y in the middle in any order. P is the string you need.

Question for 1 December 2014: 
A domino is a tile that has two positive integer numbers on it, or one number and a blank, where each number is drawn from numbers below and including the maximum number specified. How many unique tiles can be created with a maximum number of 12 on the set of dominos?

(c) ChiPrime 2014

Solution: 
This is a trick question - there are two tricks here. First, remember that though the maximum number in the set of dominos is 12, there is a blank (or zero) as well that needs to be factored in. So the number of dominos with two distinct numbers is given by 13C2=13!/(2!11!)=13*12/2=13*6=78. But that is not all. Recall that in a box of dominos, there is also one domino for each number that has two of the same number on it. This special case gives us 13 more dominos, with digits blank|blank, 1|1, 2|2, ..., 12|12 on them, for a total of 78+13=91 dominos in the box.

Question for 29 November 2014: 
[Quora] What is the probability of selecting two numbers x and y from the entire set of Real Numbers, such that x+y=5?

Solution: 
Thinking geometrically, this is the probability of picking a random point in the x-y plane such that it lies on the line x+y=5. This probability is a very small number, equal to zero for all practical purposes.

(c) ChiPrime 2014

Question for 21 November 2014: 
Given a square A with integer length side s has the same area as circle C with integer length radius r, where both the side and the radius are measured in the same units, what is the relationship between s and r?

(c) ChiPrime 2014

Solution: 
This question is asking whether you can "square a circle" and the answer to that is that it is impossible, per the detailed explanation in the article here.

Question for 15 November 2014: 
You are standing on a ladder with 11 steps to go to the top. You can either go up one step or two steps at a time. In how many different ways can you climb these 11 steps?

(c) ChiPrime 2014

Solution: 
Let us first find the maximum number of two step moves we can make with 11 steps left. This is obviously 5. So the different sets of moves to chose from are all the permutations of:
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], [2, 1, 1, 1, 1, 1, 1, 1, 1, 1], [2, 2, 1, 1, 1, 1, 1, 1, 1], [2, 2, 2, 1, 1, 1, 1,1],[2, 2, 2, 2, 1, 1, 1], [2, 2, 2, 2, 2, 1].
y
Permutations of n objects, not all distinct are given by:
if there are n1 objects of one type, n2 of another, n3 of a third, ... such that n1+n2+...+nk=n,
then, permutations=n!/(n1!*n2!*...*nk!).

So our answer is: 1+10!/9!+9!/(2!7!)+8!(3!5!)+7!/(4!3!)+6!/5!=1+10+36+56+35+6=144 ways.

(c) ChiPrime 2014

Question for 12 November 2014: 
[due to Martin Gardner?] ABCD-A'B'C'D' is a cube where ABCD is a square A is the origin, and AB, AD, and AA' are coincident with the x-, y-, and z- axes respectively. BB', CC' and DD' are parallel to AA'. What is the measure of angle A'C'D?

Solution: 
Both A'C' and C'D are diagonals of their respective surfaces, as is A'D. So triangle A'C'D is an equilateral triangle, and the angle A'C'D is 60 degrees.

(c) ChiPrime 2014

Question for 9 November 2014: 
In how many ways can different cubes' faces be painted with three colors (say red, yellow and blue), painting two sides with each, so you get distinct color configurations where reorienting a colored cube will not result in another cube from the set?

(c) ChiPrime 2014

Solution:
Take a cube, paint opposite planes with the same color. This is one.
The second cube, paint three pairs of two adjacent sides each separated by a single edge, with the same color.
Next, take three other cubes, paint the first one with two opposite faces red, then the two pairs of remaining adjacent sides with yellow and blue respectively. Then paint the second of these three cubes with opposite faces colored yellow, and two pairs of remaining adjacent sides with red and blue respectively. And finally, the third of these three with opposite faces colored red and two pairs of remaining adjacent sides with yellow and blue respectively.
With this set of five cubes as a basis, you can achieve all other configurations by reorienting cubes from this set.

Challenge question to interested programmers:
Write a program to find the above solution. Not too easy!

(c) ChiPrime 2014

Question for 6 November 2014: 
What is the probability of selecting a random three digit number such that the three digits in order from left to right, are in geometric progression? What is the probability if the "in order" restriction were removed?

(c) ChiPrime 2014

Solution: 
For both cases, all numbers of type ppp where p is a digit, satisfy the condition with common ratio=1.
For the first case, numbers like 124, 139, 248, 469 and their palindromes qualify. Giving us 17 numbers that qualify from 900 numbers, for a probability of ~0.019.
For the second case, in addition to the numbers above, distinct permutations of digits of qualifying numbers also qualify, so we also get 142, 193, 214, 241, 284, 319, 391, 412, 428, 482, 496, 649, 694, 824, 913, 946. (each 3 digit number has 3!=6 permutations, of which 2 are already covered previously, so 4 more cases exist for each of the numbers with different digits = 4*4=16). So a total of 33 (=17+16) numbers qualify for a probability of 33/900=~0.0367

You can also write simple code to solve for this as below:

import os, sys;

cnt=0;
r,u=[],[];

for i in range(100,1000):
 s=str(i);
 a,b,c=int(s[0]),int(s[1]),int(s[2]);
 z=[int(s[0]),int(s[1]),int(s[2])];
 z.sort();
 m,n,p=z[0],z[1],z[2];
 if b!=0 and c!=0 and a/float(b)==b/float(c): r+=[i];
 if n!=0 and p!=0 and m/float(n)==n/float(p): u+=[i];
 cnt+=1;

print "The probability with the in-order restriction:", float(len(r))/cnt;
print "The probability without the in-order restriction:", float(len(u))/cnt;

(c) ChiPrime 2014

[2021] 1000+ Free GRE/GMAT Quant Problems in Computer Adaptive Test Format

Adaptive tests are on the rise. These usually employ a ratchet function that increases the level of difficulty when a question is answered correctly, and presents easier questions when a question is answered incorrectly. The test then presents every candidate with the same number of questions in the allotted time, just scores easy, medium, and hard questions with different number of points each, and the final score is meant to represent one measure of the competence of the candidate in the area being tested.

copyright free image from pexels.com

Here is an example of an adaptive quant test of the type that is commonly administered to GRE and GMAT candidates. Use it free. 

The test there gives you 5 questions at a time, and then gives you an indication of the total time you took to answer the questions as well as how you did when compared to the rest of the people who took the test. Of course, as you progress through the test, being adaptive, there will be a bump up or down depending on whether you answer a question correct or wrong.

copyright free image from pixabay.com

The tests are 5 questions each so you can fit at least one into your busy day. It pulls randomly from a pool of 1000+ questions, so the likelihood that you see a question repeat is small - depending of course on how many tests you take on the site. The hard questions can be really hard though, so be prepared to focus, spend some mental energy, and work through it. 

In another post in this blog, I discuss top 10 tips on how to prep to do well on the quant sections of competitive examinations. 

Incidentally, if you are looking at going to interviews for a quantitatively focused job, this might be another resource that could be useful. Here's a youtube video where ChiPrime solves the problem: 

A circle C of radius R is such that its center is inside a square of side 2R. The smallest and largest probabilities of picking a point in S such that it also lies in C are?

There are many other problems relevant to GMAT/GRE Quant prep that are solved in that channel as well - some easy, some not so easy, just like you're likely to see on the test. Good luck! 

Rise of the Machines, or Why I can never trust Facebook with my content

Famous quote from the Facebook CEO about people who trust him is here. Pays to keep that in mind as you read the below.

Recently there was a bit of a hue and cry over some "research" that Facebook did using their user base. Apparently, in an effort to determine how users react to positive and negative messages they see in their daily feeds and how this influences the kinds of messages they themselves post to the social media network, Facebook researchers presented some of their audience with negative messages and others with positive ones, then saw that it was indeed the case that the messages people were exposed to did in fact influence the said people's posts going forward.

This isn't the first time Facebook is accused of something like this. Why, just a couple of years ago there was another set of news stories about how Facebook tried to influence their users' choices regarding whether or not they checked the donor option on the backs of their drivers licenses. However that was largely viewed as a positive example of peer pressure and was analyzed extensively here, here, here, and here. 

The latest scandal, reported here among other places, just goes to show that people (and by this I mean smart people who work together at large corporations, who think they are smarter than the average person outside their firm), will misuse data they have available to them unless they are legally prohibited from doing what they think they can get away with. In many cases, the existing laws are not designed to account for the fact that so much data can be aggregated at any one place. Companies like Facebook, and Google in particular, have so petabytes or more of data at their disposal, collect as much of the good machine learning, data analysis, programming and analytics talent as they can, and what they can do with the two things together makes it very scary indeed.

Before companies like Google grew to the size they are now, or had access to data or talent like they do today, Telecom companies in the USA, the likes of Sprint, Verizon, AT&T etc had the opportunity to build similar kinds of databases and services to leverage off of them. However, regulations pertaining to phone companies were still quite stringent, and many of these firms felt gathering and using user data without explicit permission being granted to them by the said users could expose them to litigation. So while many of the kinds of services we see today were available in telecom research labs even in that period, they were usually not deployed in the real world without explicit opt-in permissions from users, which led to their proliferation being very limited.

That said, between Google and Facebook, if one relies on mechanical data mining and adaptive algorithms such as those implemented in Google Now, while the other relies on the honesty and good intentions of human researchers, I for one would prefer the former, given machines are less likely to use my data with a particular end in mind such as testing psychological behavior in the aggregate across large user populations. Even given this however, best not to have anyone use my data against me at all. If I need something, I will pull it myself from the Internet. The network, learning too much about me to deliver what I might need before I need it is extremely creepy indeed, especially if I have to petition some company to get my data "forgotten".

"Those who surrender freedom for security will not have, nor do they deserve, either one."
                                                                                                              -- Benjamin Franklin
The same can be said about Freedom and Convenience.

Notice a new phenomenon? Earlier when you bought a phone under contract, it used to feel like your phone company owned the device. Now when you buy a phone, if it is a Google phone or an iPhone, even without a contract, it feels like you're leasing the device from one of those companies. When you buy a computer running Windows 8, it feels like you're leasing the device from Microsoft - you even need a Hotmail account to sign in to it. Why? Aren't you paying enough money to buy your phone or computer outright? Feels like a step backward into a different set of walled gardens to me. 

Sample behavioral interview questions

Sample Behavioral Interview Questions

1.       Tell me about yourself.

2.       Why should we hire you? Why should we not hire you?

3.       What are three of your greatest strengths? Weaknesses?

4.       Tell me about a time when you had to work with someone you did not get along with. How did you handle the situation? (conflict management)

5.       Tell me about a time when you had to overcome a significant challenge at work. How did you manage?

6.       Describe a situation when you had to deliver bad news or report a significant problem with a project to your boss or to a client.

7.       Which one of your accomplishments are you most proud of and why? Tell me about a time when you failed.

8.       If there was one thing you could change about your resume’ what would it be and why?

9.       What was the hardest decision you have ever had to make? How did you manage that situation?

10.   One of your direct reports, while an excellent worker, is not a cultural fit with the firm. Describe what you would do to remedy the situation.

11.   Tell me about the project (preferably from your resume’) you are most proud of, your role in it, the challenges you faced, and the learnings you gleaned from it.

12.   Tell me something about yourself that is not on your resume’.

13.   What is your ideal job? What kind of manager would you like to report to?

14.   If we offered you the job right now, would you take it? Why or why not?

15.   What did you do in terms of extra-curricular activities? Any volunteering or social activities?

16.   Tell me about your most favorite and least favorite classes in college. Why those particular ones?

17.   Who is your favorite <person from field you’re interviewing for>? Why? If you could pick one person living or dead to have dinner with, who would it be, and what would you talk about?

18.   Have you ever been in a situation where you were asked to do something you weren’t sure was morally right? Explain how you handled it.

19.   Tell me something from your resume’ that, in your opinion, makes you stand out from the candidate pool for this position.

20.   Did you ever have a major conflict with a boss or other authority figure? Tell me about it.

21.   Are you interviewing at other places? In other industries? Why do you want to work at our firm or in our industry?

22.   Tell me what your understanding is of what someone employed in the position you are interviewing for, would do on a day to day basis.

23.   If I spoke to your boss or co-workers today, what are some adjectives they would use to describe you?

24.   You are working on a project where the team lead (you feel unfairly) repeatedly rejects every idea you put forward. What would you do?

25.   A colleague of yours has stolen your work, presented it as her own and has gotten promoted for it. What would you do?

26.   Do you have any questions for me?

Want to ace GMAT or GRE Quant? Try these

Quiz 1
Quiz 2
Quiz 3

New!!!: ChiPrime Prep on Reddit!

Want more? Try this free app: Simple GRE/GMAT Math Test
Or this website that hosts the same content in mini-quiz format:  GRE/GMAT Simple Quant
Or in adaptive quiz format (Beta)!

Want to prepare for the verbal section of the GRE? Try this: GRE Word Test (new link!!! different quiz every time you visit)

Still more practice? Try this book. Questions get much harder as you progress. Suitable for IIT-JEE screening test preparation too.

100 Sprints to Math Success: Conquer the Quant Section of the GMAT and the GRE

Programming Language Questions

These are purely questions about programming languages themselves along with a little about data structures and applications thrown in for a little additional flavor. For more puzzle type or coding level questions, please see my other post on "Quant Interview Questions". What follows are questions one can typically expect to be asked in phone-screens or in early warm-up for technical interviews. This is a very non-exhaustive list, I will add more to these as time permits.

1. what is a procedural language? a functional language? what is the difference between the two?
2. what is a pointer? what is an array? when would you use one or the other?
3. what is garbage collection? give an example of where this might be used.
4. what is an object? a class? what is a class variable?
5. what is a virtual function? a pure virtual function?
6. what is the difference between a method and a function?
7. what is a partial function? give me an example.
8. what is a friend function?
9. what is a mix-in?
10. what is inheritance? what is multiple inheritance?
11. can you illustrate with an example how you would implement multiple inheritance in Java? in Python?
12. what is introspection? can you illustrate with an example?
13. can you think of any language that would allow you to create a variable from a text string a user types in at a program prompt? how would you implement this? (hint: this is easily done in Python)
14. what is the difference between passing a variable into a function by reference vs. by value?
15. what is a static variable? what is a class variable? what does the C-keyword "volatile" indicate? where is it used?
16. how can you tell the direction of stack growth on your computer? incidentally, does this tell you about the direction of stack growth on your computer, or given the context of your compiler?
17. what is a dictionary or hash table? give an example of its use.
18. what is an interface? what does serializability mean?
19. what does a pickling operation represent? how would you use it?
20. what is a hashing function? how would you use it?
21. what is operator precedence? what is operator overloading?
22. what is polymorphism? illustrate with a simple example.
23. what are software patterns? give me a simple example.
24. what is TCP/IP? what is a socket?
25. when would you use TCP vs. UDP? can you have two separate programs listen on the same socket, one for TCP and the other for UDP, at the same time?
26. what is a list comprehension?
27. what is a lambda expression?
28. what is the most efficient method to sort input data that is guaranteed to be neither sorted nor reverse sorted?
29. what is the most efficient method to find an element in a long list of data elements?
30. (***) what is a Bloom filter? how is it used?
31. (***) what is a Kalman filter? how is it used?
32. explain a socket life-cycle at the server side (bind, listen etc...) for a multi-threaded server. do the same at the client side. 
33. what is an assert? what is exception handling?
34. what is a critical section? what is the pigeonhole principle?
35. what is a semaphore? when would you use setjmp and longjmp in C?
36. what is a Turing Machine? what is the Turing Test?
37. what does a try-finally block let you do in Java?
38. what is a "Duff's device"? How would you implement a case statement in Python? 
39. what is recursion? explain with an example.
40. how would you write a function that takes multiple, variable number of arguments. illustrate with an example.
41. what is idempotence?
42. what is the difference between public, private and protected variables in a class?
43. what is a structure? a union? a typedef? an enum?
44. what is a generic? what is a template? how would you use them?
45. what is a list? a stack? a deque? a tree? how would you build a tree in Python?
46. what is a livelock? what is a deadlock? what is the difference between the two?
47. what does the term "thread-safe" mean to you?
48. can a program be a client and a server at the same time? give an example of how this might work.
49. what is monkey patching? in what kinds of languages could this work?
50. explain the difference between final, finalize, and finally in Java.
51.