I said it was rhetorical

I also knew that wouldn't stop you. :-)

Personally, I look for diversity of experience - more languages/environments is better.

"Depends on how fast it *needs* to be"

Here everything is optimized for speed. RAM is cheap. Volumes are really high though. This is the first place I've ever worked where maximum performance software was really important.

"Or if you just want a solution and RAM is not a problem, read the whole thing into a HashSet and get O(1) lookups straight from the string you read in. "

Around here *money* is not a problem for hardware as long as you're buying off the rack (no exotics). With that answer I'd ask for a quick estimate of RAM required in the worst case of all SSN's being populated. What is the overhead of a HashSet (I have no idea without doing research)?

"Actually, the best way might be: allocate 125M of RAM, and on startup flip the corresponding bit to 1 for each SSN you read in. When you get a request, convert the SSN to long or whatever, divide by 8, look up the byte, and bitmask off the remainder to see if the SSN is valid. That way you don't have to keep any of the actual SSNs in memory at all, and your question is more or less moot. ;-)"

Yep, bit vector is the best answer (smallest and fastest).

"I've personally never been in a situation like that with SSNs, though. :-)"

That's a real program at a real company where I once interviewed in San Diego. The question generally produces the nice thought process you wrote down. It lets me see the thinking pattern.

Most frequent answer from soon to be rejected candidates is to suggest a binary tree, then fail to be able to calculate the memory requirements of the fully populated structure. They get tangled up in trying to figure out memory partitioning algos to swap to disk too.

The CD sounds intriguing but I don't know how applicable it is. We use very little Java and the stuff I need coded isn't even a web app.

Sorry, Beep. ;-)

Diversity is good, but the scripting languages seem to bring out the more curious, problem-solving types. Most people who can't be arsed to learn a scripting language for the hell of it also can't be arsed to do a lot of other things.

This place is all about speed, too. We get thousands of pricing ticks a second, and those explode into huge calculations. And updates have to be as near to real time as possible.

The CD doesn't sound too useful, other than as an example. We've also given applicants a shell login and had them code in a C++ environment on a server here. You could probably do the same thing with Oracle if that's what you're looking for. Just make sure you trust your sysadmins to get the permissions right. :-P

The key is to make them do an actual project in an environment where they can be comfortable, in order to get an idea of how they would work on the job as opposed to in an interview.

I put a copy of the problem up for general perusal at [link|http://www.mr-anderson.net/stuff/PROJECT.html|http://www.mr-anders...tuff/PROJECT.html] if anyone is interested.

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