I think if you don't specifically train for competitive programming, an average LC hard is going to take you many days, assuming you solve it at all. A lot of them depend on knowledge of algorithms that most people will literally never use for anything professionally, ever.

As much as we like to talk about algorithms, it's pretty rare that anything more interesting than DP comes up at work unless you are doing optimization research or work in a niche domain like bioinformatics.

Interviewing someone with an LC hard is a colossal waste of time unless the position you are filling is like "senior staff swe: performance and optimization"