Solution: Course Schedule II

Statement

Let’s assume that there are a total of $n$ courses labeled from $0$ to $n-1$. Some courses may have prerequisites. A list of prerequisites is specified such that if $Prerequisites_i = {a, b}$, you must take course $b$ before course $a$.

Given the total number of courses $n$ and a list of the prerequisite pairs, return the course order a student should take to finish all of the courses. If there are multiple valid orderings of courses, then the return any one of them.

Note: There can be a course in the $0$ to $n-1$ ...