亚马逊笔试 2019 年 5 月软件开发工程师 I

您总共需要学习 n 门课程，标记为从 0 到 n-1。

有些课程可能有先决条件，例如，要参加课程 0，您必须先参加课程 1，这表示为一对：[0, 1]

鉴于课程总数和先决条件对列表，您是否有可能完成所有课程？

Examples:
Input: 2,
[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.
Input: 2, [[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.