This will vary a lot with company size and problem domain. But strictly looking at SNR, my experience is that you get a lot more value out of doing mock code reviews than setting Leetcode problems.

Example mock code review (or quasi pair code review):

- look at 400-600 lines of code that are problem domain specific

- If onsite, we leave the room for an agreed time period where they can review the code on their own

- The code is purposefully sprinkled with layers of defects, basic language issues, footgun issues, test quality/coverage, styling, and architectural design

- Just let them talk through their findings, then pick their brains to understand how deeply they understand their own claims

- Stronger candidates will go from the basics up to design and more meta topics. Weaker ones usually only touch the surface