KACTL

KACTL (the KTH Algorithmic Contest Template Library) is an extensively curated and high-performance C++ algorithms library created by the competitive programming team at the Royal Institute of Technology (KTH) to serve as a trusted, battle-tested codebase for algorithmic contests, programming competitions, and general algorithm development. The repository aggregates dozens of concise implementations of essential data structures, numerical methods, graph algorithms, string processing tools, computational geometry routines, and optimization techniques, all designed with speed, correctness, and compactness in mind. Instead of reinventing algorithms on the fly during contests like ACM-ICPC or Codeforces rounds, competitors can import exactly the component they need — whether a segment tree with lazy propagation, a minimum cost flow solver, or a fast Fourier transform — and focus their energy on problem logic and strategy.