course_schedule_ii.py

def findOrder(numCourses, prerequisites):
  """
  :type numCourses: int
  :type prerequisites: List[List[int]]
  :rtype: List[int]
  """
  if prerequisites:
    d = {}
    for i in range(numCourses):
      d[i] = set()
    for c in prerequisites:
      d[c[0]].add(c[1])
    q = []
    for i in d:
      if not d[i]:
        q.append(i)
    res = []
    while q:
      n = q.pop()
      res.append(n)
      for c,r in d.items():
        if n in r:
          d[c].remove(n)
            if not d[c]:
              q.append(c)
    if len(res) != numCourses:
      return []
    return res
  else:
    return [i for i in range(numCourses)]