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g0201_0300.s0207_course_schedule.readme.md Maven / Gradle / Ivy

207\. Course Schedule

Medium

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.

*   For example, the pair `[0, 1]`, indicates that to take course `0` you have to first take course `1`.

Return `true` if you can finish all courses. Otherwise, return `false`.

**Example 1:**

**Input:** numCourses = 2, prerequisites = [[1,0]]

**Output:** true

**Explanation:** There are a total of 2 courses to take. To take course 1 you should have finished course 0. So it is possible. 

**Example 2:**

**Input:** numCourses = 2, prerequisites = [[1,0],[0,1]]

**Output:** false

**Explanation:** There are a total of 2 courses to take. To take course 1 you should have finished course 0, and to take course 0 you should also have finished course 1. So it is impossible. 

**Constraints:**

*   1 <= numCourses <= 105
*   `0 <= prerequisites.length <= 5000`
*   `prerequisites[i].length == 2`
*   0 <= ai, bi < numCourses
*   All the pairs prerequisites[i] are **unique**.