Problem
Course Schedule
Medium- graphs
- topological-sort
Courses are labeled 0 to numCourses - 1. Each pair [course, prereq] in prerequisites says that prereq has to be finished before course can be started.
Return true if the courses can be finished in some order that respects every pair, and false if they cannot. The answer is false exactly when the pairs form a cycle.
- Input
numCourses = 5, prerequisites = [[1, 0], [2, 1], [4, 2], [4, 3]]- Output
true- Explanation
0, 1, 2, 3, 4 is a valid order, because every course comes after the courses it needs. Course 4 has two prerequisites, which is not a cycle.
- Input
numCourses = 4, prerequisites = [[1, 0], [2, 1], [0, 2]]- Output
false- Explanation
course 1 needs 0, course 2 needs 1 and course 0 needs 2, so the three wait on each other in a circle and none can start. Course 3 is free, but all four courses have to be finished.
- Input
numCourses = 3, prerequisites = []- Output
true- Explanation
there are no pairs, so any order works.
Constraints:
0 <= course, prereq < numCoursesfor every pairprerequisitesmay be empty
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