Given a castle with rooms named after flowers where each room has an instruction to the next room, write an algorithm to find the rooms containing treasure.

This problem can be modeled as a directed graph where rooms are nodes and instructions are edges. To find treasure rooms, we can simulate traversing the castle. Start from an arbitrary room and follow the instructions. Keep track of visited rooms to detect cycles. If a room is a treasure room, add it to our result list. Since each room has exactly one outgoing edge, the structure will be a set of components, each consisting of a cycle with trees leading into it. We can iterate through all rooms, and for each unvisited room, start a traversal. If we encounter a treasure room during traversal, mark it. If we detect a cycle, we can determine if any room in the cycle is a treasure room. Repeat until all rooms are visited.