Prerequisite Cycle OA

The OA used the original LeetCode Course Schedule prompt: given course prerequisites, decide whether all courses can be completed. It appeared in a two-question, medium-difficulty HackerRank assessment. Requirements Given numCourses and prerequisite pairs, decide whether it is possible to finish all courses. Each prerequisite pair means one course depends on another course being completed first. Return a boolean answer. Use standard Course Schedule prerequisite-cycle semantics. Notes The main risk is cycle handling in a directed graph. Make the direction of each prerequisite edge explicit before coding. A clean answer can use either indegree processing or DFS state coloring; explain the invariant rather than only writing code. This appeared as one of two OA questions in a 60-minute, non-camera HackerRank-style assessment. Preparation Implement both an indegree-queue version and a DFS coloring version. Test no prerequisites, a simple chain, a two-node cycle, a disconnected graph, and duplicate prerequisite pairs.