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CONTRIBUTING.md

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+Keeping a daily feed of functional algorithm implementations is not
+a task for a one-human-army. That's why contributing to this project is highly encouraged.
+
+If these moving words haven't convinced you to loan your precious time to "the cause", you can always consider some of the following reasons:
+
+First: Implementing algorithms in Scala, constraining yourself to functional
+programming is one of the funniest puzzles you'll ever met.
+
+Besides, from a selfish standpoint, you will:
+
+* Get the credit in the daily tweeter feed.
+* Train your problem solving skills.
+* Discuss about the approaches to solve problems and learn along the way.
+* **ONLY THIS MONTH!** Earn a [Hacktoberfest](https://hacktoberfest.digitalocean.com/) t-shirt by contributing to an open source project.
+
+But, more important are some of the reasons to support the Scala & Functional Programming communities:
+
+* Spread the word about category theory, performance, data structures and other Scala libraries.
+* Demonstrate that Functional Scala can be quite a performance beast.
+* Spread the knowledge on algorithmic design.
+
+### The contributor guide to @DailyAlgorithm
+
+Accepted contributions will:
+
+ - Be 100% [referentially transparent](https://en.wikipedia.org/wiki/Referential_transparency).
+ - Offer clean reusable code. Preferably generic.
+ - Come with clear **time complexity** upper bound, at least for the average case.
+ - Include a Twitter handle or other mean to refer the author in the feed.
+
+**NOTE:** Feel free to open PRs even when those might not meet some or all of the requirements above described. The maintainer(s) will offer as much help as possible.
+
+Find and example [here](https://github.com/pfcoperez/algorithmaday/pull/9).
+
+Outstanding ones will:
+
+ - Show functional patterns usage. Such as category theory application.
+ - Introduce new technologies related to: Functional programming (and/or category theory) patterns, data structures, software testing and performance measurements.
+ - Include one or more diagrams explaining the contribution, they will be used in the Twitter feed.