#+PROPERTY: STUDY_DECK_02
* TODO 0210. Course Schedule II :medium:
:PROPERTIES:
:NEETCODE: [[file:../../roadmap.org::*0210. Course Schedule II][0210. Course Schedule II]]
:END:

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] = [a_{i}, b_{i}]~ indicates that you *must* take course ~b_{i}~ first if you want to take course ~a_{i}~.

 - 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*.

*Example 1:*


#+begin_src
Input: numCourses = 2, prerequisites = [[1,0]]
Output: [0,1]
Explanation: There are a total of 2 courses to take. To take course 1 you should have finished course 0. So the correct course order is [0,1].
#+end_src


*Example 2:*


#+begin_src
Input: numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]
Output: [0,2,1,3]
Explanation: There are a total of 4 courses to take. To take course 3 you should have finished both courses 1 and 2. Both courses 1 and 2 should be taken after you finished course 0.
So one correct course order is [0,1,2,3]. Another correct ordering is [0,2,1,3].
#+end_src


*Example 3:*


#+begin_src
Input: numCourses = 1, prerequisites = []
Output: [0]
#+end_src


*Constraints:*

 - ~1 <= numCourses <= 2000~

 - ~0 <= prerequisites.length <= numCourses * (numCourses - 1)~

 - ~prerequisites[i].length == 2~

 - ~0 <= a_{i}, b_{i} < numCourses~

 - ~a_{i} != b_{i}~

 - All the pairs ~[a_{i}, b_{i}]~ are *distinct*.

** TODO Approach
Write your approach here.

** TODO Python
#+begin_src python
class Solution:
    def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
#+end_src

** TODO C++
#+begin_src cpp
class Solution {
public:
    vector<int> findOrder(int numCourses, vector<vector<int>>& prerequisites) {
        
    }
};
#+end_src