OA with two LeetCode medium-ish questions. One was algorithmic, and one was a math question. Pretty sure they send it to everyone, then resume screen after, depending on your results.
Leetcode
The following metrics were computed from 33 interview experiences for the Citadel SWE Intern role in United States.
Citadel's interview process for their SWE Intern roles in the United States is extremely selective, failing the vast majority of engineers.
Candidates reported having very good feelings for Citadel's SWE Intern interview process in United States.