LeetCode #210 - Course Schedule II

There are a total of n courses you have to take, labeled from 0 to n-1. Some courses may have prerequisites, for example, to take course 0 you have to first take course 1, which is expressed as a pair: [0,1]. Given the total number of courses and a list of prerequisite pairs, return the ordering of courses you should take to finish all courses. If it is impossible to finish all courses, return an empty array.

Problem Statement

def findOrder(numCourses: int, prerequisites: List[List[int]]) -> List[int]:

Example 1

Input: numCourses = 4, prerequisites = [[2,0],[1,0],[3,1],[3,2]]
Output: [0,1,2,3]
Explanation: There are multiple correct orders, but one possible order is [0, 1, 2, 3].

Example 2

Input: numCourses = 2, prerequisites = [[1,0],[0,1]]
Output: []
Explanation: There's no way to complete the courses because they depend on each other.

Constraints

• The input prerequisites is a graph, where the number of nodes is numCourses and the number of edges is the length of prerequisites.