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AC(AtCoder) Library

AC Library is the official library of AtCoder. This repository manages the contents of AC Library.

You may refer to the following links for more details:

The documents of master branch are as follows:


Our goal of this project is to achieve that

  • Enable every AtCoder users to use this library with minimum efforts of studying about PC
  • Maximize convenience for the usage in competitive programming. We completely ignore other usages.
  • No bugs. This is a fantasy, but we pursue this.

By this policy, we ignore some manners of C++ intentionally. For example,

  • we don't use size_t, but use int.
  • Segtree handles function pointers, not functional objects.
  • and so on...

Direction of this project

We haven't decided whether we should increase this library's contents or not because there are pros and cons. If you are interested in this topic, please join the discussion in The Announcement on Codeforces.

For now, we are not planning to add new features, and we use this repository only for

  • collecting issues
  • recording the changelogs
  • versioning our releases


We accept issues/PRs only from AtCoder users.

We would appreciate it if you would report our mistakes like a typo, or, more importantly, bugs!

As mentioned above, we haven't decided which way to go. Therefore we are not accepting feature requests for now, and issues will be closed.


You can view the newest version of AC Library in The Announcement on AtCoder page.

You can also see all versions in The Release page.


This library is released under the CC0, except for the third-party libraries that are located under /document_(en|ja)/lib directory. Please refer /document_en/lib/ for details.