Programmers: Your favorite interview questions

[FightAndLive]

I haven't seen one these posts yet on this forum(if there is forgive me : )), but I figured to help out more people looking for programming work I would start a post for employers who are looking to hire new programmers what kind of questions you guys ask. I'm the technical director at a small game studio in LA, and were expanding so I also looking to see what everyone does so I can adjust accordingly.

Some of the basic questions I ask are:

What is global scope/local scope.

What is a template class

What is inheritance/polymorphism/etc.

Than some really basic logic stuff like whats a recursive function, etc etc.

Than I begin to ask a couple questions that are kind of off the wall because one thing I noticed is College graduates from big schools such as UCLA 9/10 can't figure stuff for themselves. Students are so used to stuff getting spoon fed to them, some of which is just nasty. One thing that really irritated me at one of the studios I worked at previously a couple of there senior programmers came to me and said "I don't know how to do xyz, can you help?" This normally is a pretty common thing, except when xyz happens over and over again and its something that easily be found by doing a quick google search.

I ask the interviewee if they can do something that 99% of the programmers out there can't do. They would obviously say I don't know, I would then ask them than to look it up for me on google and write out basic steps on how to get it done. Lets say I ask them how to register a custom Debug Engine in Visual Studio, first google search for "visual studio custom debug engine" which turns up http://msdn.microsof...4(v=vs.80).aspx , with a link to http://msdn.microsof...(v=vs.110).aspx. Even though the information on the latter article is actually wrong if they copied that I would be so happy. I've had guys sit there for 10 minutes struggling, and I feel that's kind of ridiculous. Every programmer in world should know how to use google :/.

Than depending on the level of the job, I would go into some more nitpicker things say in Unreal, Unity, D3D, whatever and if someone didn't know the answer I would ask them to google it and give me an explanation. I had actually had one guy who didn't graduate from a college, straight out of high school and he didn't know something I asked him, and than he immediately asked if he could go on google and look it up. I actually hired him on the spot and he ones of the best programmers I've ever had.

Anyway what kind of stuff do you guys ask?

[Andre S. Veteran]

I'm not an interviewer, but if I was I think I would always start with the Fizz Buzz Test. Filtering out 99.5% of incompetents with such a simple question is appealing :)

Questions I've been asked:

For a game programming, C++ position:

1) Explain what is a conditional breakpoint and how to create one.

2) Write a function in C++ to inverse the endianness of an unsigned integer.

3) You have a cloud of points in 2d. Design an algorithm to draw the smallest circle that contains all the points.

For a C# position:

1) What's the most important difference between C# and C++? (IIRC I answered that so thoroughly he didn't ask any other questions :p)

[HSoft]

For a C# position:

1) What's the most important difference between C# and C++? (IIRC I answered that so thoroughly he didn't ask any other questions :p)

This one is kinda subjective. Different people can have different answers and (potentially) they could all be correct.

[WelshBluebird]

Not to do with interviews, but a quick reply to what you mentioned in your post.

In terms of using google and such, one problem is company conventions, or company specific libraries etc etc.

I just started a job as a developer, and my company has quite a lot of internally developed libraries that we can use (without any real documentation that says what the libraries include). There are also quite a lot of conventions and "done things" which restrict what kind of things we can do, and where in the code things should go. Obviously as a new starter I don't know everything that is included in the libraries or all of the conventions.

If I am struggling with something I will try to figure it out myself at first, and if that fails use google. But sometimes I will also double check with a colleague just to make sure I am not going down totally the wrong way and wasting an hour or whatever.

[seethru]

I'm a lead developer at a games studio as well.

Typically we start with FizzBuzz and move from there. I focus more on finding out how the person thinks. I'm less concerned with syntax because that can be taught, while teaching someone to think logically is near impossible.

[El Marto]

I'm not an interviewer, but if I was I think I would always start with the Fizz Buzz Test. Filtering out 99.5% of incompetents with such a simple question is appealing :)

We use FizzBuzz and it literally filters out 95% of candidates for iOS positions as well as firmware engineers. Shocking how many people cant do it.

[neufuse Veteran]

"Write a program that prints the numbers from 1 to 100. But for multiples of three print ?Fizz? instead of the number and for the multiples of five print ?Buzz?. For numbers which are multiples of both three and five print ?FizzBuzz?."

I've never seen that test used in interviews myself, but gawd, if you can't do a modulus program..... and 99.5% don't get it? seriously?!

We don't even start that simple, we start out with a complex problem and see how they squirm... if they get frustrated we have an issue, if they stop think it out and write down a plan, we have a possible winner even if they don't get it, they still took the correct starting route

[rfirth]

I've never seen that test used in interviews myself, but gawd, if you can't do a modulus program..... and 99.5% don't get it? seriously?!

I've been asked that question. As soon as you give the solution using modulus, they ask you to do it again without using modulus/multiplication/division.

Microsoft asked me this question:

Given a matrix of numbers where all numbers are monotonically increasing from left to right across every row, and monotonically increasing from top to bottom down every column, design an efficient algorithm to search for an element in the matrix.

Then there is always the usual linked list questions.

[El Marto]

"Write a program that prints the numbers from 1 to 100. But for multiples of three print ?Fizz? instead of the number and for the multiples of five print ?Buzz?. For numbers which are multiples of both three and five print ?FizzBuzz?."

I've never seen that test used in interviews myself, but gawd, if you can't do a modulus program..... and 99.5% don't get it? seriously?!

We had a woman last week open up word and write out 1-100 manually. before then going through and adding the fizz-buzz. I was literally in amazement.

[neufuse Veteran]

We had a woman last week open up word and write out 1-100 manually. before then going through and adding the fizz-buzz. I was literally in amazement.

on a simple problem, that is overkill, but after seeing how some colleges teach programming, it doesn't suprise me....

we actually did some more "annoying" things like giving people problems in ML and LISP after giving them an introduction to it and asked them to solve a problem..

if you can take a language like LISP after given a quick tutorial on it and use it, we've definatly take you to the top of the list

learning languages on the fly is definatly something few can do

my favorite problems are data structure problems, and giving a change stacking issue where you can only flip side by side coins but they can only flip if their size is greater, how to store this, how to sort it, how to sort it efficiently etc, drives some nuts

[neufuse Veteran]

I've been asked that question. As soon as you give the solution using modulus, they ask you to do it again without using modulus/multiplication/division.

Microsoft asked me this question:

Given a matrix of numbers where all numbers are monotonically increasing from left to right across every row, and monotonically increasing from top to bottom down every column, design an efficient algorithm to search for an element in the matrix.

Then there is always the usual linked list questions.

see something like that would get me because I'd have to say what's your definition of monotonically, unless you had a lot of math experience you might not of heard it before to know its a function between ordered sets.. if you gave me the definition sure could code it.

I'm a languages person, I can pick up languages quickly and learn efficiencies fast... math wise though beyond Discrete math sometimes my mind goes haywire... I hated calculus, I understand it, I just hate it.. something about calculating the volume of a sea shell always drove me nuts and finding the integral that creates it ugh

[neufuse Veteran]

I've been asked that question. As soon as you give the solution using modulus, they ask you to do it again without using modulus/multiplication/division.

if they would tell me to do it without mod/mul/div then I'd do it in binary step by step and see if they remember how that all works using bitwise masking.. not hard to take a number in binary AND it with a mask of the binary version of the divisior - 1 to get the remainder then check from there (i know this is still a modulus by hand, but it shows you understand the workings of it at the binary level)

[Andre S. Veteran]

if they would tell me to do it without mod/mul/div then I'd do it in binary step by step and see if they remember how that all works using bitwise masking..

You don't necessarily need binary:

using System;

class Program {

    static void Main() {
        int fizz = 0;
        int buzz = 0;
        for (int i = 1; i < 100; ++i) {
            if (++fizz == 3) {
                Console.Write("Fizz");
                fizz = 0;
            }
            if (++buzz == 5) {
                Console.Write("Buzz");
                buzz = 0;
            }
            if (fizz != 0 && buzz != 0) {
                Console.Write(i);
            }
            Console.WriteLine();
        }
    }
}[/CODE]

[neufuse Veteran]

You don't necessarily need binary:

using System;

class Program {

	static void Main() {
		int fizz = 0;
		int buzz = 0;
		for (int i = 1; i < 100; ++i) {
			if (++fizz == 3) {
				Console.Write("Fizz");
				fizz = 0;
			}
			if (++buzz == 5) {
				Console.Write("Buzz");
				buzz = 0;
			}
			if (fizz != 0 && buzz != 0) {
				Console.Write(i);
			}
			Console.WriteLine();
		}
	}
}[/CODE]

yes, but binary is another way of doing it...

[El Marto]

Interesting site for fizzbuzz solutions :) http://rosettacode.org/wiki/FizzBuzz

[Andre S. Veteran]

This one is kinda subjective. Different people can have different answers and (potentially) they could all be correct.

I don't see it like that. The most important difference is that one is based on .NET and the other isn't. Everything else - the type system, garbage collection, assemblies, etc - derives from that.

[neufuse Veteran]

I don't see it like that. The most important difference is that one is based on .NET and the other isn't. Everything else - the type system, garbage collection, assemblies, etc - derives from that.

what if someone says well C++ can also use the CLI if you wanted to? then you have C++ in .NET under the CLI :) ... but yeah polymophism from the base type "object",GC etc etc

if you want to get technical managed C++ probably should be called MC++ but MS still calls it C++ basically

[+Majesticmerc MVC]

Some of my more memorable ones:

Test questions:

• Given the following algebraic equations, determine the value of x and y (simultaneous equations in my case, intended to test math proficiency).
  
• Given a rope laid around the equator of the earth, how long is the rope? If you raise the rope 3 feet from the ground all the way round, how much longer would the rope be?
  
• Design an algorithm that will print all the numbers between one and a 50,000,000 that are divisible by 13. (easy to write, but a surprising number of people don't write it efficiently).
  
• Given the following code (taken from the company's codebase), what would be your best guess as to its purpose.
  
• Given the following C++ code, list all the places an exception could be thrown.
  
• Given the following code, what efficiency improvements do you feel could be made?
  
• Given two integer variables, A and B, how could you swap their values without using a third variable? (This is my favourite. It wasn't actually given to me, but to my housemate at the time. He didn't get it, but the interviewer gave it to him to do on the train home, he figured it out on the train and emailed the answer to the interviewer, subsequently got the job :p)
  
• Implement x sorting algorithm using pseudo code or a language of your choice.
  

Verbal questions:

• What has been your most memorable project, and why?
  
• What is your favourite programming language, and why? What do you feel are it's strengths. What are it's weaknesses?
  
• What do you know about our company? (seriously, if a person didn't care to even find out what your company does, they weren't serious about joining, IMO. I admit that I fell for this one when applying for my work placement at university for a company.)
  

[firey]

So, I had never heard of the FizzBuzz test, decided to give it a shot, was not hard at all, my solution was less than elegant, and after reading on here and remembering module I shortened the code up by about 10 lines total.

so try 1:

		static void Main(string[] args)
		{
			for (double i = 1; i < 101; i++)
			{
				Console.WriteLine((isMultOfThree(i) && isMultOfFive(i) ? "FizzBuzz" : (isMultOfThree(i) ? "Fizz" : (isMultOfFive(i) ? "Buzz" : i.ToString()))));
			}
			Console.ReadKey();
		}
		static bool isMultOfThree(double num)
		{
			double val = num / 3;
			if (val.ToString().Contains("."))
				return false;
			else
				return true;
		}
		static bool isMultOfFive(double num)
		{
			double val = num / 5;
			if (val.ToString().Contains("."))
				return false;
			else
				return true;
		}


//The two if's could be shortened to just return (!(num / 5).ToString().Contain("."));
[/CODE]

And using modulo

[CODE]
static void Main(string[] args)
{
for (double i = 1; i < 101; i++)
{
Console.WriteLine((isMultOfThree(i) && isMultOfFive(i) ? "FizzBuzz" : (isMultOfThree(i) ? "Fizz" : (isMultOfFive(i) ? "Buzz" : i.ToString()))));
}
Console.ReadKey();
}
static bool isMultOfThree(double num)
{
return num % 3 == 0;
}
static bool isMultOfFive(double num)
{
return num % 5 == 0;
}
[/CODE]

I am not really that efficient, and I like to keep code clean (hence separate functions).

And reading the coding challenges from majestic. I decided to try the Integer one. This was how I did it in C#, 3 lines of code for swapping. Not sure if it will always work, but it does for me.

[CODE]
int a = 100;
int b = 200;


//Point is to make a == b and b == a
Console.WriteLine('\n' + a.ToString());
Console.WriteLine(b.ToString());

b += a;
a = b - a;
b -= a;

Console.WriteLine(a.ToString());
Console.WriteLine(b.ToString());
[/CODE]

[Andre S. Veteran]

what if someone says well C++ can also use the CLI if you wanted to? then you have C++ in .NET under the CLI :) ... but yeah polymophism from the base type "object",GC etc etc

C++/CLI is a different language with its own syntax.

[neufuse Veteran]

C++/CLI is a different language with its own syntax.

It's not a complte differnet language, Managed C++ is just extensions to the C++ language that include grammatical and syntactic extensions

[Andre S. Veteran]

It's not a complte differnet language, Managed C++ is just extensions to the C++ language that include grammatical and syntactic extensions

"C++/CLI should be thought of as a language of its own (with a new set of keywords, for example), instead of the C++ superset-oriented Managed C++ (MC++) (whose non-standard keywords were styled like __gc or __value)." http://en.wikipedia.org/wiki/C%2B%2B/CLI

C++/CLI has its own ECMA standard distinct from the ISO C++ standard, it is not designed by the same comittee, it has a different syntax, a different compiler, it compiles for a different platform.

[zeta_immersion]

if else man .. ftw ... then again the most i did was arrays

[+Fahim S. MVC]

Haven't coded professionally for some time (about 5 years) but nice to know I aced the FizzBuzz test first time I tried it just a few moments ago in Java.

[Brandon Live Veteran]

It's not a complte differnet language, Managed C++ is just extensions to the C++ language that include grammatical and syntactic extensions

Managed C++ and C++/CLI are actually different things :-) Well, the latter replaced the former. And yes, at least C++/CLI is just a set of standardized extensions to C++.

Stroustrup's thoughts on it are an interesting read:

http://www.stroustrup.com/bs_faq.html#CppCLI

[rfirth]

And reading the coding challenges from majestic. I decided to try the Integer one. This was how I did it in C#, 3 lines of code for swapping. Not sure if it will always work, but it does for me.

			int a = 100;
			int b = 200;


			//Point is to make a == b and b == a
			Console.WriteLine('\n' + a.ToString());
			Console.WriteLine(b.ToString());

			b += a;
			a = b - a;
			b -= a;

			Console.WriteLine(a.ToString());
			Console.WriteLine(b.ToString());
[/CODE]

It's probably worth mentioning why that won't always work... what happens if a = MAX_INT - 2 and b = MAX_INT - 3? The addition of a and b will overflow...

Can you think of another operator you can use?