The interview was literally nothing but back-to-back brainteasers and leetcode-challenges for 3 hours straight.
I didn't get the job even though I only failed to solve one problem, and looking back I think that the problem was in fact unsolvable and they wanted me to come to that conclusion rather than admit that I couldn't solve it in my head.
Google, just like all other FAANG companies, uses a lot of Leetcode-style questions and there's no tendency for this to change so far. The thing that Google does is that they ban interview questions which were exposed on Leetcode, so they could've meant that you won't be given a question that is known to Leetcode crowds.
> looking back I think that the problem was in fact unsolvable
As for the unsolvable problem, this is weird, but when the company has tens of thousands of active interviewers, chances are that one of them will surely ask some bullshit question, and there is a very low chance that someone will ever let that interviewer know that they're not doing a good job. The lottery aspect always exists here.
(Though personally I don’t think giving a truly unsolvable problem in an interview without warning that this may be unsolvable is a reasonable test of anything, but a cruel experiment)