{ "data": { "question": { "questionId": "210", "questionFrontendId": "210", "categoryTitle": "Algorithms", "boundTopicId": 1464, "title": "Course Schedule II", "titleSlug": "course-schedule-ii", "content": "

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you must take course bi first if you want to take course ai.

\n\n\n\n

Return the ordering of courses you should take to finish all courses. If there are many valid answers, return any of them. If it is impossible to finish all courses, return an empty array.

\n\n

 

\n

Example 1:

\n\n
\nInput: numCourses = 2, prerequisites = [[1,0]]\nOutput: [0,1]\nExplanation: There are a total of 2 courses to take. To take course 1 you should have finished course 0. So the correct course order is [0,1].\n
\n\n

Example 2:

\n\n
\nInput: numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]\nOutput: [0,2,1,3]\nExplanation: There are a total of 4 courses to take. To take course 3 you should have finished both courses 1 and 2. Both courses 1 and 2 should be taken after you finished course 0.\nSo one correct course order is [0,1,2,3]. Another correct ordering is [0,2,1,3].\n
\n\n

Example 3:

\n\n
\nInput: numCourses = 1, prerequisites = []\nOutput: [0]\n
\n\n

 

\n

Constraints:

\n\n\n", "translatedTitle": "课程表 II", "translatedContent": "

现在你总共有 numCourses 门课需要选，记为 0 到 numCourses - 1。给你一个数组 prerequisites ，其中 prerequisites[i] = [ai, bi] ，表示在选修课程 ai 前 必须 先选修 bi 。

\n\n\n\n

返回你为了学完所有课程所安排的学习顺序。可能会有多个正确的顺序，你只要返回 任意一种 就可以了。如果不可能完成所有课程，返回 一个空数组 。

\n\n

 

\n\n

示例 1：

\n\n
\n输入：numCourses = 2, prerequisites = [[1,0]]\n输出：[0,1]\n解释：总共有 2 门课程。要学习课程 1，你需要先完成课程 0。因此，正确的课程顺序为 [0,1] 。\n
\n\n

示例 2：

\n\n
\n输入：numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]\n输出：[0,2,1,3]\n解释：总共有 4 门课程。要学习课程 3，你应该先完成课程 1 和课程 2。并且课程 1 和课程 2 都应该排在课程 0 之后。\n因此，一个正确的课程顺序是 [0,1,2,3] 。另一个正确的排序是 [0,2,1,3] 。
\n\n

示例 3：

\n\n
\n输入：numCourses = 1, prerequisites = []\n输出：[0]\n
\n\n

 

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