Hacker Rank

Hacker Rank这个网站汇集了各方面的编程挑战供你hack，人工智能，机器学习等等方面，hacker可以在上面展现自己的智慧，每道题有各种语言支持，c/c++/python/haskell等等。可以查看排名什么的。

官方地址 https://www.hackerrank.com/

来自官方的邮件介绍
HackerRank is a hub for hackers to solve a wide variety of challenges, ranging from quick 10-min problems to big data, Artificial Intelligence, Machine Learning challenges, and many more. We're also working with engineering- focused companies in various domains to provide interesting real-world (real data?) problems to make the experience much better.
Every problem solver has one type of challenge and level of difficulty that really intrigues him - either to solve or learn something new.

尝试了下第一题，是九宫格，有难度。

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