This is an initial phone screen and in this context this a valuable approach. This is one level past fizzbuzz. 'Can you code something past "hello world"?' is what they're looking for. There's nothing worse than an onsite with somebody who just cannot code at all.
The particular example is bad, though, because there’s room for a massive algorithmic insight. There’s an obvious-enough but terribly inefficient way to do it, and a fancy efficient algorithm that either you know or you don’t. If given this question I would middle through the inefficient way, aware that there must be a better algorithm out there that’s eluding me, and I’d probably get a “vaguely pass” mark, but the kid fresh out of college who has spent the last three months doing leetcode study will regurgitate the correct solution and pass with flying colours.
(Once in a while maybe a complete genius takes the test and reinvents the good algorithm on the spot, but only gets the same grade as the diligent student, for his effort.)
Too many basic coding screens seem to rely on some algorithmic insight. I would rather give a candidate a complicated-but-straightforward problem (like a super-fizzbuzz that takes half a page to describe,with a bunch of complicated rules and exceptions to those rules) because that’s closer to what a real world programming task looks like. No room for a clever insight, just translate the problem statement, carefully, into code, and test whether it runs correctly.
> because that’s closer to what a real world programming task looks like
To make it even closer, you'd have to have people coming in at various points with contradictory updates to the task, impossible requests, an overbearing managerial diktat, etc.
