They’re IQ tests, it’s that simple.
Not only correct solution but also generate alternatives to showcase what other things you know to get strong-hire.
Example:
This problem was asked in Google: https://leetcode.com/problems/cat-and-mouse/
It is actually based on a paper [1]. Plus it seems it is expected that one needs to know about 'alpha-beta' pruning algos for such problems.
If you solve this using dfs ... its basically gtfo
[1] https://www.semanticscholar.org/paper/Undirected-Cat-and-Mou...
Or which ones are young and single with no responsibilities outside of work. Which is likely a feature, not a bug.
This one, for instance is expected to be completed in 30 minutes. I spent 2 hours on it yesterday and failed most test cases. I'm a failure.
Its true on some degree, that you need some intelligence, but I have a few close friends who are FAANG, they are definitely not the best developers I've ever worked with, only difference is they really really cared about getting into FAANG. Getting into FAANG was basically their life ambitions, so they dedicated literally all there spare time to it.