Course Schedule (#207)
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.
Return true if you can finish all courses. Otherwise, return false.
Company Tags: Google, Uber
Core Concept: Graph, Topological Sort