You Think Google Has Hard Interview Questions? Try EFI.

 
The job interview - "Oops!",
by Big Fat Rat.

Google is famous for its hard interview questions . When I lived in the USA I used to listen to Car Talk on NPR, a radio show that had its own hard weekly questions in its "puzzler" segment.. When I was browsing the Car Talk web site I saw their hardest "puzzler" .

A hundred prisoners are each locked in a room with three pirates, one of whom will walk the plank in the morning. Each prisoner has 10 bottles of wine, one of which has been poisoned; and each pirate has 12 coins, one of which is counterfeit and weighs either more or less than a genuine coin. In the room is a single switch, which the prisoner may either leave as it is, or flip. Before being led into the rooms, the prisoners are all made to wear either a red hat or a blue hat; they can see all the other prisoners' hats, but not their own. Meanwhile, a six-digit prime number of monkeys multiply until their digits reverse, then all have to get across a river using a canoe that can hold at most two monkeys at a time. But half the monkeys always lie and the other half always tell the truth. Given that the Nth prisoner knows that one of the monkeys doesn't know that a pirate doesn't know the product of two numbers between 1 and 100 without knowing that the N+1th prisoner has flipped the switch in his room or not after having determined which bottle of wine was poisoned and what colour his hat is, what is the solution to this puzzle?

EFI at Night, Foster City,
by cool_blue_dog.

The problem sounded difficult but familiar, and sure enough ....

it was written by a man named Alan B. at EFI, Inc

I had worked at EFI when I was in the USA and when I interviewed software engineering candidates I asked challenging interview questions, as was common practice there . We interviewers had had to answer difficult questions to get employed there in the first place so we had  seen it from both sides.

Googleplex,
by Laughing Squid.

Alan B's question brings back some memories. I am glad I didn't get it at my interview.

A web search found my favorite EFI interview question on an interview questions web site .
How hard can Google interview questions be?