Course Schedule

You get numCourses courses, numbered 0 to numCourses - 1. You also get a list prerequisites of pairs [a, b]. A pair means you must finish course b before you start course a.

Return True if you can take all the courses in some order. If you can't, return False.

Example 1:

Input: numCourses = 5, prerequisites = [[1, 0], [2, 1], [4, 3], [4, 2]]
Output: True
Explanation: Each arrow goes from a course to a course that needs it:
    0 → 1 → 2 → 4
            3 → 4
Course 4 needs both 2 and 3.
Taking the courses in number order, from 0 to 4, works.

Example 2:

Input: numCourses = 4, prerequisites = [[1, 0], [2, 1], [3, 2], [1, 3]]
Output: False
Explanation: The arrows 1 → 2 → 3 → 1 form a loop.
Course 1 waits for course 3.
Course 3 waits for course 2.
Course 2 waits for course 1.
Course 0 is fine, but the other three can never start.

Example 3:

Input: numCourses = 3, prerequisites = []
Output: True
Explanation: No course has a prerequisite, so any order works.

Constraints:

• 1 to 100,000 courses.
• Up to 100,000 pairs.
• Both courses in a pair are valid course numbers.
• The two courses in a pair are different.
• No pair appears twice.