Citadel SWE intern round 1: min cost to hire K workers, with AI assistant allowed

Interviewed at Citadel for SWE intern, July 2026, first technical round (CoderPad + Zoom). Format: ~20 minutes resume grilling/systems knowledge, then a ~20-minute hard problem with an AI assistant allowed. The problem just a reworded version of LC 857-style, Minimum Cost to Hire K Workers. Spent most the time tracing through test cases and ended up solving the problem with ai and explaining how the outputted answer worked (I ran out of time so this is what I ended up doing lol). I've also done the second of the two first rounds that they do so I might do a follow up post on that.