Important! Check LICENSE! All rights reserved, no permission is granted! The code here is protected by default copyright rules: you may view and read it for personal study, but please do not copy or reuse complete solutions directly! It's a matter of ethics. It’s published for learning and reference only, also as a showcase of my approach, not a bundle of copy-paste ready answers.
I only add solutions that I consider highly above average or hard in difficulty or personally interesting, i.e. things that taught me something non-trivial. This is not a solution graveyard. : - )
Here are the most, in my opinion, notable solutions:
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0435 - reachable-state enumeration + interning (dedup) + Chinese remainder theorem + subset sum + NFA → DFA (subset construction) + Miller-Rabin primality test.
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0932 - centroid decomposition + combinatorics (counting/aggregation over a tree with centroid splits).
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1394 - assignment problem + Hungarian algorithm + augmenting paths + primal-dual potentials.
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0866 - st-numbering + graph biconnectivity + ear decomposition.
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0981 - boolean expressions theory + functional bases (logic parsing + basis properties).
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0026 - caching + Belady (farthest next use) + heap.
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0117 - sweep line technique + prefix sums.
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0567 - DSU + 4-connectivity on a grid + path compression (connected components).
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0046 - parity + minimax (game-style reasoning).
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wc21 - computational geometry + enumeration / backtracking.
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1399 - Capacitated Vehicle Routing Problem (CVRP/VRP) + TSP on subsets (Held–Karp bitmask DP) + greedy heuristics.
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2122 - combinatorics + hamming contribution trick + generating functions + NTT under 40961.
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2042 - segment tree + lazy range assignment + Manacher on small buffer.
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1829 - routing tables + LPM + bitmasks (IPv4 AND mask) + DFS traversal + rule equivalence checking.
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1598 - DSA + finite fields + modular arithmetic + fast modular exponentiation + BSGS + crypto break via small parameters.
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2196 - computational geometry + point-in-convex-polygon (O(log N)) + point-to-segment distance + Minkowski sum / offset (Steiner formula).
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All tasks
As you might have guessed, most of the problems in this repository come from two major Russian competitive programming training platforms:
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ACMP - it’s a long-running site with a huge archive of problems. Alongside solid classic tasks, there are plenty of quirky and non-standard problems - sometimes with unusual constraints, odd formulations, or obscurity in the sense of being more about decoding the statement and handling edge cases than applying a clean textbook algorithm. The site is maintained by Sergey N. Belyaev (listed as the author/admin in ACMP materials) and is associated with the Krasnoyarsk Krai Palace of Pioneers and Schoolchildren.
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Yandex CodeRun - it’s Yandex’s developer training platform: an online problem catalog and curated selections to practice programming across multiple tracks (e.g., backend, frontend, mobile, ML/analytics). It also has community features and periodic challenges/events. The platform is operated by Yandex LLC (ООО «Яндекс»).
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Timus Online Judge - a classic ICPC-flavored problem archive and online judge. It hosts Internet versions of many contests held at Ural Federal University (UrFU) and includes problems from regional ICPC/NEERC-style contests (and related training events). The site is created and administered by students and graduates of UrFU.
- C/C++ - my primary languages. I use them at work, I enjoy them, and most competitive programming tasks are a natural fit for this toolset.
- C# - here mostly out of curiosity. I occasionally poke the .NET ecosystem/infrastructure just because I`m interested.
- PHP - work-driven: I deal with the PHP ecosystem from the runtime/engine and extensions side (C mostly). We run static analysis on the engine/addon code, triage findings, and do fuzzing. Sometimes I write some PHP to better understand how it behaves in practice.
- Python - the baseline language. It’s the quickest way to prototype, validate ideas, or write tiny utilities. I use it when I don`t wanna be bothered.
This repository is mostly competitive-programming style code: consistent, fast to write/read under time pressure, and focused on the algorithm rather than ceremony.
What you’ll see a lot (generally in C/C++ files):
- A small personal template:
#include <bits/stdc++.h>, fast I/O, and a few tiny helpers/aliases. - Short, consistent naming:
n, m, k,ans,g,dp,dist, etc. The goal is to reduce visual noise. I don`t like long words. - Shorthands/macros like
rep,sz,all,pb,fi/se,rsr(...)to compress boilerplate (looping, container ops, pair access). This is intentional and comes from a low-level mindset: make common patterns dense and recognizable. I don`t like long expressions. - A deliberate trade-off: this style is great for contests and personal notes, but I do not claim macros are best practice for production.
I keep a small CI pipeline that’s intentionally close to my setup. The goal is reproducibility and “works on my machine” parity - if it compiles here, it’ll compile on my box too.
- Environment: GitHub Actions runs everything inside a
debian:bookworm-slimcontainer. - C/C++ (LLVM Clang only): every
*.cppis compiled as C++20, every*.cas C11 (-O2 -pipe; C links with-lm). Each file is built standalone and outputs go intobuild_ci/- this catches missing headers, accidental dependencies, etc. - C# (Mono): compiles every
*.cswithmcs(-optimize+) intobuild_ci_cs/. - VB (Mono): compiles every
*.vbwithvbc(ormono .../vbc.exefallback) (-optimize+) intobuild_ci_vb/. - Python: syntax/bytecode sanity via
pypy3 -m compileall. - PHP: lint via
php -l.
This is a build/lint sanity check, not a full correctness test. Maybe one day in the future I will decide to organize full-fledged tests.