[softawre]

Agreed. I have a spot open now and have done ~10 interviews in the past couple months. We do something much easier - "write a function to return whether a string has a balanced number of parenthesis". Essentially a number, +1 for (, -1 for ), return false if <0, return true if 0 at end of loop.

20% of our applicants pass this, and they all go through a phone screen first..

[gcheong]

Shouldn't that be return false if != 0?

[RogerL]

It is not required that the interviewer be able to pass his own question, silly. ;)

[throwawayinterv]

20% is a very suprising number...

Would something like this pass (maybe with some comments and test cases)?

    1 @tailrec
    2 def hasBalancedParens(s:String, open:Int):Boolean = {                                               
    3   if(s.length == 0)           open==0
    4   else if(s.charAt(0) == '(') hasBalancedParens(s.tail, open+1)
    5   else if(s.charAt(0) == ')') open>0 && hasBalancedParens(s.tail, open-1)
    6   else                        hasBalancedParens(s.tail, open)
    7 };

Or should line 5 halt the loop? What if line 4 did not contain open>0 at all?

If this answer fails (modulo any stupid mistakes; idk if it even compiles), you might consider being much more specific about the desired average runtime complexity.

If this answer passes but would fail if line 4 was modified, you might consider re-writing your problem text to include either "Feel free to ask for clarifications" or "A string has balanced parentheses only if every closing parenthesis is preceded by an opening parenthesis". People tend to not treat interviews like normal interactions, and interview questions don't have a surrounding context so it's hard to determine what it means for an answer to be correct.

[FilterSweep]

balanced number, or balanced syntactically?

I think it's a fair question..... but "())))(((" would fail in the second condition

[wdmeldon]

I think merely asking this question would be qualification enough.

[throwawayinterv]

As I suggested in another comment, it might be in general bad advice to try to get people to ask clairfying questions about non-contextual interview problems. If you want to measure social adeptness / willingness to ask for clarification -- which are important! -- consider interview questions that have a "role playing" component or actively invite the interviewee to ask questions.

[cema]

In my experience, clarifying questions are important. In this case, for instance, we have two different problems (well, not too different, but still).

[aiokos]

Is it 20% to generate something like this, which balances parentheses without syntax? If so that is seriously surprising.

  function getBalance (parenStr) {
      var count = 0;
      for (var i = 0; i < parenStr.length; i++) {
          if (parenStr[i] === '(') { count++; }
          else if (parenStr[i] === ')') { count--; }
      }
      return count === 0;
  }

[hibikir]

Most programmers that have any business getting hired should be able to do that. The problem is that when you interview people, you don't get a good sample of the population: The worse you are, the more interviews you have to do, because you get declined a whole lot.

In a previous job, a question like that would not even get a 20% pass rate, but it also have a lot to do with where we were sourcing our employees: If you are talking to generic contracting firms that employ people in giant, generic behemoths, you WILL get a lot of terrible candidates from them. From the powerpoint architect that hasn't written a line of code in weeks, to people that just had a job at big megacorp, and did the minimum possible not to get fired (and, in some of those corps, that's really little).

It got that bad that there were employer patterns that we considered resume black flags: Spent one year in MasterCard? Well, they hire pretty much anyone for a year, and they just don't get renewed, so we will understand that experience as 'you weren't good enough to work there, and most people there suck'.

[abustamam]

wouldn't that just see if there are an equal amount of parentheses, not whether or not they're balanced?

For example, your code would return true for ")())((" even though nothing is balanced. I was thinking more of a stack; push to stack only on opens, pop on closes, if we get a close before an open is on the stack, then we return false.

But I only thought about it for a few minutes so it's rather rudimentary.

[make3]

20%!!!??!?! wtf!

[matwood]

In other jobs we have given very simple coding exercises to do before the interview (fizzbuzz like or simpler), and have gotten solutions that do not even compile.