I applied through university. The process took 1 day. I interviewed at Citadel (New York, NY) in Feb 2019
Interview
Three first round interviews, all statistics and game theory type questions. No fit or behavorial questions.
Also gave a couple of brain teaser, including the famous rolling die and also a question about chess.
Interview questions [1]
Question 1
Played a made-up card game and asked me what the probability of the next card would be, and the decision I should make