I'm going to preface this by saying this was NOT what I was asked in my Meta interview whatsoever - that would be a breach of my NDA and I am totally a law-abiding citizen. In fact, I've never told a lie in my life, can you believe that?
Anyway, here's the list of questions a friend of mine was asked in his loop:
Q1: LC1424 Diagonal Traverse 2 / LC498 Diagonal Traverse
The variant is asked where you must print out the anti-diagonal of the given matrix. Exactly like This.
Q2: LC270 Closest Binary Search Tree Value
A variant was asked where it's an integer not a double.
Q3: LC253 Meeting Rooms 2
No variant asked here. But beware there are many, many variants like the "Employee Free Time" one (which is also similar to LC23).
Q4: LC1249 Min Remove to Make Valid Parentheses
A follow-up variant was asked to do it in space complexity. No coding was required, just a verbal explanation.
Please know that if you resist and try to code it out, the interviewer will immediately stop you. Don't try.
Q5: LC138: Copy Linked List with Random Pointer
...A variant was asked to copy a binary tree. Here's another Post of someone being asked it.
Q6: LC121 Buy Sell Stock
A variant was asked of flights and departures. Here's a Reference Post.
As of time of writing, I feel like Meta's asked slightly different variants (e.g. maximum cost between 2 arrays, return flight must be within K days). Also thanks to all the people sharing these variants!
In case you were wondering,
YOE? 9
Level? E5, they wanted to push E6 though.
Location? US
System Design? Ad Click Aggregator
Good luck everyone! Let me know if you have any other questions and I'll try to help out.