WePay interview questions

How to know if a given string contains characters only without using inbuilt functions

Onsite: - trapping rain water - scrabble board (given board with words on it, dictionary of words, a new word to add, and letter points --> find optimal placement for new word) - no system design, but one round in onsite to talk about work experience where sysdesign might be relevant. In this round, my interviewer was VERY insistent that I describe the challenges in every project we talked about to the point that it was impossible to have a conversation. He was pushing pretty hard and picked apart anything I mentioned with some variation of "But is that even challenging though?" I tried to give him specific examples multiple times, but it was like he was never satisfied...We used the full hour for this round, so I inevitably ran out of "challenges" to describe and felt he was fairly passive aggressive and argumentative. Conceptually, this round is better than straight up asking system design, but in practice was exhausting and will depend on your interviewer's need to conversationally torture you. - "real life question" to emulate a work task w/ classes, functions, constructor; should be pretty easy :)