Course Schedule

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 <= 2000` - `0 <= prerequisites.length <= 5000` - `prerequisites[i].length == 2` - `0 <= ai, bi < numCourses` - All the pairs prerequisites[i] are **unique**.