Leetcode - Course Schedule II

Question

There are a total of numCourses courses you have to take, labeled from 0 to 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 ai.

• 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.

Ideas

• Given the problem, you can convince yourself that this is a graph problem since we are essentially given edges between nodes of classes where we want to find the order that we need to take the classes
• Therefore, finding the order of nodes implies Topological Sort
• In the event that we have a cycle, no path to take numCourses is possible, therefore we should return []

Solution