Course Schedule II

Given a list of n courses labeled from 0 to n-1, some courses may have prerequisites. These are expressed as a two-dimensional integer array prerequisites where prerequisites[i] = [ai, bi] indicates that course ai must be completed before course bi. Return a possible order of courses you should take to finish all courses. If it is not possible, return an empty array. Example 1: Input: numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]] Output: [0,1,2,3] or [0,2,1,3] Example 2: Input: numCourses = 2, prerequisites = [[1,0]] Output: [0,1] Example 3: Input: numCourses = 2, prerequisites = [[1,0],[0,1]] Output: [] Constraints: 1 <= numCourses <= 2000 0 <= prerequisites.length <= numCourses * (numCourses - 1) prerequisites[i].length == 2 0 <= ai, bi < numCourses ai != bi All the pairs [ai, bi] are distinct Example Input 4 [[1,0],[2,0],[3,1],[3,2]]