Course Schedule II
LeetCode 210 • Medium • Topological Sort
prerequisites[i] = [a, b] means take course b before a. Return any valid ordering of all courses, or [] if impossible (cycle).
TimeO(V+E)
SpaceO(V+E)
Step0/0
Waiting
In queue
Processing
In order
Ready
Demo:
numCourses=4, prereqs [[1,0],[2,0],[3,1],[3,2]]. Kahn’s algorithm builds a take-order list.