Topological Sort for Course Ordering (Course Schedule II-like)

You are given the total number of courses n (labeled 0..n-1) and a list of prerequisite pairs prerequisites, where each pair [a, b] means you must take course b before course a. Return any valid ordering of courses (an array of length n) that satisfies all prerequisites. If it is impossible due to a cycle in the directed graph, return an empty array. Requirements: Must detect cycles in a directed graph. Target time complexity close to O(n + m), where m is the number of prerequisite relations. Typical interview constraints: 1 <= n <= 2 * 10^5 0 <= len(prerequisites) <= 2 * 10^5 Example: Input: n = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]] Output: [0,1,2,3] (or [0,2,1,3]) Example Input 4 4 1 0 2 0 3 1 3 2 Output 0 1 2 3