Comments on: A Simple Audition for Developers

By: Karl Meissner

Karl Meissner — Wed, 22 Jun 2005 22:52:53 +0000

Hi JR.
I spoke to you at SPIN. Nice talk.
Thanks.
over an hour?!?!ok just make a point, it is a single line of c code
void cpy( char* d, char* s){ for(;*d = *s; ++d, ++s); }
ingnoring the 3 to 5 easily checked error conditions…which is important since this kind of code was responsible to the buffer overflow attacks awhile back
but over an hour? yeeessh
when I do interviews though I tend to make my questions a lot harder. I have had people walk out.
I am not being mean.
Its just that there is about a 10x productivity difference between the top %25 of developers and the bottom %25.
here are some hard questions
given two dates(day, month,year), how many days are there between them
sort a list of numbers. The list is larger then can fit in ram
implement a binary search on a list of integers
implement the game Scrabble…
but these are too hard for phone screen. Any good ideas for a quick phone screen questions?
The other area I was looking to improve was easy ways of figuring out teamwork, good people skills, chemistry…not sure it can be tested
other then by trotting the canidate out in front of the other team members… a lot of work that way though.
Karl

By: Miles Barr

Miles Barr — Mon, 13 Jun 2005 14:24:01 +0000

Jason I agree there are several potential ways to do this in Java but I don’t want to force the developer to come up with solutions that would otherwise fail a code review. In Java you shouldn’t copy strings, just pass the same reference around. If I saw any of those snippets in actual production code, I would be concerned about the developer’s understanding of strings in Java.
A spin on the question would be to present several string copy solutions and ask them to say which one is best, but then it becomes a bit of a trick question.
A problem I’ve had coming up with short, yet potentially deep, questions in Java is the amount of dependency on libraries. Every programming question in Java comes down to what library you choose to use, the trick is not to turn the question into a rote-memorization of the APIs.

By: Zorkerman

Zorkerman — Thu, 09 Jun 2005 23:59:56 +0000

I had an interview when I was asked in java to write on a piece of paper the “hello, world” program in java. I responded with the “Why?” question as well, and the interviewer said that many appliants cannot write it without and IDE.
I offered to try and throw in some complexity for complexities sake just so I could show off a little, but she just wanted to see the program.
Of course the Big O notation part didn’t go over so well.

By: Deepak Surti

Deepak Surti — Tue, 07 Jun 2005 23:35:00 +0000

I think one more thing that needs to be added is the “ability to design with the langugage”. Questions like string-copy are great to find out if he can work with the langugae. Next should be if one can design with the language?
Ex design scenario::In our organizaion sales managers are given targets under different goal heads. At the end of every month they do submit the actuals vis a vis the expected.
Tell me how will you implement this feature : “calculating monthly targets” in say::java, ruby,..c# whatever?
Answers are illumintating.

By: Jason

Jason — Tue, 07 Jun 2005 18:32:05 +0000

I think it’s a great Java question — look at all the potential solutions Miles came up with.
The fact that candidates get an hour to work on this makes me feel like a genius.

By: Faisal N. Jawdat

Faisal N. Jawdat — Tue, 07 Jun 2005 17:24:14 +0000

I wonder how much of the success of this question depends on the language. In C this is (or should be) easy. In Perl you might get into some functions that a lot of people spend their entire professional lives never touching (substr?).

By: Xuemin Guan

Xuemin Guan — Tue, 07 Jun 2005 14:52:30 +0000

Spot on!

By: Miles Barr

Miles Barr — Tue, 07 Jun 2005 14:47:44 +0000

I like the idea of a developer audition as part of the interview process. The String-Copy example has a nice balance of complexity and pit falls against time. But it is a very C style question and doesn’t really make sense for languages where strings are a first class object. e.g. in Java you wouldn’t copy a string because they are immutable, so it would be silly to make a copy. But if you had to make a copy you could do:
String original = “original”;
String copy = new String(original);
or a bit more perverse
int len = original.length();
char[] copyBuffer = new char[len];
for (int i = 0; i < len; i++) {
copyBuffer[i] = original.charAt(i);
}
String copy = new String(copyBuffer);
or
String copy = String.copyValueOf(copyBuffer);
or course this is wrong because it will throw an exception:
String copy = original.clone();
But for me the correct answer for write a string copy in Java is, there is no need because strings in Java are immutable. Which brings me to my question, have you come across any similar questions for Java that would be suitable for an interview?