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I recently bombed an interview with a graph theory question. I hadn't done any real from-scratch implementations of that stuff, but I do know enough to discuss

I recently bombed an interview with a graph theory question. I hadn't done any real from-scratch implementations of that stuff, but I do know enough to discuss it and pseudocode it. They were disappointed, they wanted to see runnable code right there on the whiteboard. I think you're right, you should know basic conceptual computer science. I felt like I did a good job of explaining that I understand enough to do a real implementation if I had to, with man pages and my IDE and so on. But nope, they wanted a piece of acrylic to be a compiler, and that's just wrong IMO.

tptacek 10y ago
I spent 2 years writing multicast routing algorithm implementations for an overlay multicast startup I cofounded. The moral equivalents of PIM sparse and OSPF. I wouldn't do it this way again, knowing what I know now, but we did LSA forwarding between nodes the same way a Cisco would flood LSAs over a set of unruly PPP DS1 links. The hard way, is what I'm trying to convey here. Anyways, I interviewed a company my friend Nate was working for, on a lark (my company was sort of winding down). First question I got: "explain Bellman-Ford routing". Bellman-Ford is one of the simplest distributed systems algorithms there is, and certainly the simplest foundation for a routing protocol (it's what the RIP protocol does). I had, prior to that interview, implemented RIP twice, in two different jobs. I totally bombed the interview! My mind just went blank. I could explain how link-state routing with shortest path graph reductions worked, but not how a much simpler algorithm worked. The interview made some clucking noises about how interesting it was to be interviewing someone who wasn't a Stanford CS student. The next interview asked me to implement Towers of Hanoi non-recursively. I refused. Obviously, I didn't get an offer.
- hawkice 10y ago
  > The next interview asked me to implement Towers of Hanoi non-recursively. What? Obviously this isn't a great interview question, but this seems massively pointless. I don't think there is an obvious way of doing this that doesn't just turn the call stack into an explicit stack (which, again, is pointless). And the recursive code is the only code that could possibly be understood by someone whose whole world isn't dominated by understanding those ~12 lines. EDIT: also, ya know. Who cares. I have not even heard of a software engineering legend where solving anything remotely similar to towers of hanoi was necessary.

tptacek 10y ago

I spent 2 years writing multicast routing algorithm implementations for an overlay multicast startup I cofounded. The moral equivalents of PIM sparse and OSPF. I wouldn't do it this way again, knowing what I know now, but we did LSA forwarding between nodes the same way a Cisco would flood LSAs over a set of unruly PPP DS1 links. The hard way, is what I'm trying to convey here. Anyways, I interviewed a company my friend Nate was working for, on a lark (my company was sort of winding down). First question I got: "explain Bellman-Ford routing". Bellman-Ford is one of the simplest distributed systems algorithms there is, and certainly the simplest foundation for a routing protocol (it's what the RIP protocol does). I had, prior to that interview, implemented RIP twice, in two different jobs. I totally bombed the interview! My mind just went blank. I could explain how link-state routing with shortest path graph reductions worked, but not how a much simpler algorithm worked. The interview made some clucking noises about how interesting it was to be interviewing someone who wasn't a Stanford CS student. The next interview asked me to implement Towers of Hanoi non-recursively. I refused. Obviously, I didn't get an offer.

hawkice 10y ago
> The next interview asked me to implement Towers of Hanoi non-recursively. What? Obviously this isn't a great interview question, but this seems massively pointless. I don't think there is an obvious way of doing this that doesn't just turn the call stack into an explicit stack (which, again, is pointless). And the recursive code is the only code that could possibly be understood by someone whose whole world isn't dominated by understanding those ~12 lines. EDIT: also, ya know. Who cares. I have not even heard of a software engineering legend where solving anything remotely similar to towers of hanoi was necessary.