210. 课程表 II

1. [题目链接](210. 课程表 II - 力扣（LeetCode）)

2. 解题思路：和[课程表Ⅰ](207. 课程表 - ouyangxx - 博客园)思路一致，只不过每次都要收集答案。

3. 代码

    
   class Solution:
       class node:
           def __init__(self):
               self.pre = 0   # 要依赖几个
               self.nexts = set()   # 能解锁哪些
    
    
       def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
    
           courses = {}
           cando = set(range(numCourses))    # 初始化，所有的课程都能够做
           for i in range(numCourses):
               courses[i] = self.node()
           for course in prerequisites:
               # course[0]不能先做  要先完成course[1]
               if course[0] in cando:
                   cando.remove(course[0])
               courses[course[0]].pre += 1
               courses[course[1]].nexts.add(course[0])
           ans = []
           while cando:
               cur_course = cando.pop()
               ans.append(cur_course)
               for next_course in courses[cur_course].nexts:
                   courses[next_course].pre -= 1
                   if courses[next_course].pre == 0:
                       cando.add(next_course)
           return [] if len(ans) != numCourses else ans