0%

### 题目描述

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`.

### 例子

#### 例子 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.

#### 例子 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 <= 10^5`
• `0 <= prerequisites.length <= 5000`
• `prerequisites[i].length == 2`
• `0 <= ai, bi < numCourses`
• All the pairs `prerequisites[i]` are unique.

### 解题思路

• 时间复杂度: `O(|E|)`
• 空间复杂度: `O(max(|E|, |V|))`

GitHub 代码同步地址： 207.CourseSchedule.cpp

GitHub: Leetcode-C++-Solution