Maybe you didn't mean to use that word but it's not about "explaining" them: you have to be able to write the code to solve a given problem, on the spot. The problem might require a familiar technique such as breadth-first search but it will need to be adapted; the problem is likely to be slightly different from anything you've seen before.
It's true that at the staff interviews i just did, LC was not required but at the staff interviews i'm about to do they will be.
I meant explain. I see explain as a superset of implement. I have met lots of people who can implement but not explain. I didn't mean a simple explanation, I mean actually going into depth about things like algorithmic complexity, memory usage, etc.
As an interviewer (granted not at FAANG) I see no value in you just proving you did an algorithm on Leet Code. You could just be passing it through rote learning. I want to make sure you understand it. Otherwise I'm just wasting your time. But that's just my interview style, I know bigger companies may be different.
> I mean actually going into depth about things like algorithmic complexity, memory usage
OK, I agree that's definitely something the candidate should be able to do. I'm just trying to point out to anyone reading that it won't be sufficient to explain an algorithm. You have to actually write code to solve a given problem. That's not the same as regurgitating code you remember from leetcode, so please don't think that. You have to apply techniques that you've learned. It's not easy, and it's not intellectually shallow.
It's true that at the staff interviews i just did, LC was not required but at the staff interviews i'm about to do they will be.