atcoder/ac-library

Health v2 · maintenance only

Adoption not part of the score

2345 stars · 268 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

The official C++ library for AtCoder, providing well-tested implementations of common algorithms and data structures used in competitive programming. It is designed for minimal learning effort and maximum contest convenience, intentionally ignoring general-purpose C++ conventions.

Use cases

• use segment trees and Fenwick trees in competitive programming contests
• compute max flow and min cost flow quickly during a contest
• use modular arithmetic and convolution helpers for math problems
• get a ready-made DSU (union-find) implementation for AtCoder problems
• avoid rewriting standard competitive programming algorithms in C++

When to choose

• you compete on AtCoder (or similar judges) in C++ and want reliable, fast standard algorithms
• you want a CC0-licensed, header-only library with zero setup effort
• you need contest-focused implementations that prioritize simplicity over generality

When to avoid

• you need a general-purpose production C++ library with idiomatic APIs (it intentionally ignores C++ conventions)
• you need features beyond the fixed algorithm set, since new features are not being added
• you work in a language other than C++

Facets

library · maturity maintenance

math cpp cross-platform atcoder competitive-programming header-only algorithms data-structures cpp

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