Are contest problems from interviews or made up?

I've never participated in LC contests before and I'm not sure how exactly they work but I've noticed that some relatively recent hard problems (~1200+ range) require more advanced techniques (ie binary lifting, bitmask dp).

I feel that these problems are from contests (I can tell by discussion). If that's true then are LC contest problems inspired by real interviews? Honestly, either is fine with me. I was just wondering.

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