KACTL
KTH algorithm competition template library
...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.