mapto store edges,
crs => [prevArr].
indegreefor every node.
- Build a
queueto store whose
indegree == 0.
- Keep iterating until queue.length === 0. And decrement the first node of queue’s indegree by 1. If it becomes
0, add it to queue. Then, add cur node to the front of
- If all indegree is 0, then return result. Otherwise, return ;
There are a total of
numCourses courses you have to take, labeled from
numCourses - 1. You are given an array prerequisites where
prerequisites[i] = [ai, bi] indicates that you must take course
bi first if you want to take course
- For example, the pair [0, 1], indicates that to take course 0 you have to first take course 1.
Return the ordering of courses you should take to finish all courses. If there are many valid answers, return any of them. If it is impossible to finish all courses, return an empty array.
Input: numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]