Had a phone screen with Facebook for E4/E5 and was told that there would be 2 questions in the beginning.
Adding two ints represented as strings. Similar to this one except it should also work for negative nos - https://leetcode.com/problems/add-strings/
Merging k-sorted lists - https://leetcode.com/problems/merge-k-sorted-lists/

Finished both in time and moving onto onsite