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I interviewed at twitter for a job working with their infra team. They had an Atlanta data center and they were interviewing me for that role to be remote out o
by leetrout 7y ago
I interviewed at twitter for a job working with their infra team. They had an Atlanta data center and they were interviewing me for that role to be remote out of Atlanta. I had to fly to SF to interview via video calls with the team in Atlanta because the manager was in SF. He told me he would prefer someone local in SF over lunch so I knew I was just filler.
After lunch interview was with a xoogler and everyone earlier warned me it would be a “google interview”. So he struts in and asks what I know about number theory. I say nothing and he tells me he was a math major and proceeded to ask math proof questions and push on the math side of things the whole time. Weirdly instead of asking how to make a Cartesian product in SQL he had this round about way of describing baseball players and teams and generating a report of games played.
So as it went on I gave up. He asked me toward the end how many prime numbers there are... I answered “optimus prime”. He looked at me and asked if I seriously wanted him to write down “optimus prime” for my answer and I swear on my life I looked at him and said “yep. Autobots roll out”.
- gunshai 7y ago>I looked at him and said “yep. Autobots roll out” Man I've been steady on the job hunt and I have to say I needed a funny story like this. Thank you. I'd like to think there is a good follow up but my guess is you got ghosted.
- leetrout 7y agoThis may sound shocking, but I did not get the job ;)
- WWLink 7y agohahahahahahahah :D I don't think it's possible to have a finite number of primes though? But it's a programming interview, so really, who gives a shit?!
- PopeDotNinja 7y agoYes, it's not possible to have finite primes. Take all the primes from 2 to N, multiply them together, and add one to get a prime. If there's always another prime, there's infinite primes!
- cion 7y agoYou don't always get a prime. For example, 4! = 2 * 3 * 4 = 24, 24 + 1 = 25, 25 is not prime. The point is that N! + 1 is not divisible by any number from 2 to N (always leaves a remainder of 1), so either it is prime, or it is divisible by something larger than N!, therefore larger than N. In the case of 25, it is divisible by 5 (> 4).
- edu 7y agoThe parent said to multiply _only the primes_ from 2 to N, and then add one not factorial plus one. In your example it would be (2 * 3) + 1 = 7, prime.
- cion 7y agoOh, sorry, didn't realize that. It still doesn't work, though, as the example of 2 * 3 * 5 * 7 * 11 * 13 + 1 = 59 * 509 shows.
- conanite 7y agoIt's a little bit more subtle. Assume that there is a finite number of primes, and P is the set of all primes p0, p1, p2... pn. If you multiply all these together and add 1, you have a number Q that's not divisible by any number in P. So P cannot be the set of all primes.
- michaelt 7y agoRight, but if you were testing N=13 as the highest prime, then (2 * 3 * 5 * 7 * 11 * 13) + 1 must either be prime itself, i.e. have no prime factors, or must have a prime factor greater than 13. And in either case, a prime greater than 13 exists - in your example, 59. This is Euclid's proof [1] and it's some 2300 years old. [1] https://en.wikipedia.org/wiki/Euclid%27s_theorem https://en.wikipedia.org/wiki/Euclid%27s_theorem