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Submission: On September 17 via manual from RU — Scanned from US
Submission: On September 17 via manual from RU — Scanned from US
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→ History
5 hours ago User -is-this-fft- inserted blog post [Tutorial] Rotating calipers
technique and its applications by asdasdqwer: inserted field blogEntryId 133763,
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31 hour(s) ago User WeakestTopology inserted blog post Snapshot of finite
calculus and using it to solve a 3000 rated problem by WeakestTopology: inserted
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2 weeks ago User Plasmatic updated blog post How to Effectively Practice CP +
Problem Solving Guide How to Effectively Practice CP + Problem Solving Guide by
SuperJ6: updated field englishName
How to Effectively Practice CP + Problem Solving Guide.
2 weeks ago User Plasmatic inserted blog post How to Effectively Practice CP +
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3 weeks ago User Dominater069 inserted blog post How to Solve Questions
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7 weeks ago User paula inserted blog post [Tutorial] Directed DFS trees (and the
Tarjan algorithm for Strongly Connected Components) by de_sousa: inserted field
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2 months ago User valeriu updated blog post [Tutorial] Li Chao Tree Extended 2
by tibinyte: updated field position 10900.
2 months ago User valeriu updated blog post using merging segment tree to solve
problems about sorted list by TLE: updated field position 91000.
2 months ago User valeriu updated blog post [Tutorial] Li Chao Tree Extended 2
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2 months ago User valeriu updated blog post [Tutorial] XOR Segment Tree by
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2 months ago User valeriu updated blog post Li Chao Tree Extended 2 [Tutorial]
Li Chao Tree Extended 2 by tibinyte: updated field englishName
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2 months ago User valeriu updated blog post Li Chao Tree Extended 2 [Tutorial]
Li Chao Tree Extended 2 by tibinyte: updated field position 12100.
2 months ago User valeriu updated blog post Push-Free Segment Tree by nikgaevoy:
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2 months ago User valeriu updated blog post Li Chao Tree Extended 2 [Tutorial]
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2 months ago User valeriu updated blog post A Slight Generalization of Push-Free
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2 months ago User valeriu inserted blog post Li Chao Tree Extended 2 [Tutorial]
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2 months ago User Tom66 inserted blog post Montgomery/Barret reduction and NTT
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2 months ago User Tom66 inserted blog post A tool for hacking rolling hashes
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3:26:39 PM, inserted field deleted false, inserted field hidden false, inserted
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2 months ago User Tom66 updated folder Testing and Polygon: updated field
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2 months ago User Tom66 updated blog post [Tutorial] Boruvka's Algorithm by
RockyB: updated field position 4300.
2 months ago User Tom66 updated blog post Algorithm Gym :: Graph Algorithms by
PrinceOfPersia: updated field position 3400.
2 months ago User Tom66 updated blog post Codeforces Updates (April-May, 2015)
by kuviman: updated field hidden falstrue.
2 months ago User Tom66 inserted blog post Codeforces Updates (April-May, 2015)
by kuviman: inserted field blogEntryId 18327, inserted field catalogFolder
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4 months ago User -is-this-fft- inserted blog post C++ STL: Order of magnitude
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4 months ago User -is-this-fft- updated blog post [Tutorial] On lambdas, C++ and
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4 months ago User -is-this-fft- inserted blog post [Bugged] Dynamic Bitsets in
GCC by bitset: inserted field blogEntryId 129454, inserted field catalogFolder
C++, inserted field creationTime May 14, 2024, 6:16:29 PM, inserted field
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5 months ago User -is-this-fft- inserted blog post [Tutorial] The sparse set
data structure by Redpo: inserted field blogEntryId 127472, inserted field
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2:41:27 AM, inserted field deleted false, inserted field hidden false, inserted
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5 months ago User -is-this-fft- inserted blog post [Tutorial] Hungarian
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26, 2024, 2:40:04 AM, inserted field deleted false, inserted field hidden false,
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5 months ago User -is-this-fft- inserted blog post Division-less Euclid's
algorithm by orz: inserted field blogEntryId 124218, inserted field
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2:39:44 AM, inserted field deleted false, inserted field hidden false, inserted
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5 months ago User -is-this-fft- inserted blog post “Log Decomposition”, a
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5 months ago User -is-this-fft- inserted blog post On implementing O(nlog(n)^2)
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5 months ago User -is-this-fft- inserted blog post [Tutorial] An elementary way
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2:33:30 AM, inserted field deleted false, inserted field hidden false, inserted
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5 months ago User -is-this-fft- updated blog post [Tutorial] Online Dynamic
Connectivity by ko_osaga: updated field catalogFolder
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5 months ago User -is-this-fft- updated blog post Link Cut Tree implementation
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5 months ago User -is-this-fft- updated blog post [Tutorial] Subtree lazy
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5 months ago User -is-this-fft- updated blog post Maintain subtree information
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5 months ago User -is-this-fft- updated blog post Link-cut tree tutorial by
ramchandra: updated field catalogFolder BLinary Searchk-Cut Trees.
5 months ago User -is-this-fft- inserted folder Link-Cut Trees: inserted field
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5 months ago User -is-this-fft- updated folder Connectivity Queries: updated
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5 months ago User -is-this-fft- updated folder Persistence: updated field
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5 months ago User -is-this-fft- updated folder Disjoint Set Union: updated field
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5 months ago User -is-this-fft- updated folder Persistence: updated field
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5 months ago User -is-this-fft- updated folder Disjoint Set Union: updated field
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5 months ago User -is-this-fft- updated folder Persistence: updated field
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5 months ago User -is-this-fft- updated folder Disjoint Set Union: updated field
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5 months ago User -is-this-fft- inserted folder Connectivity Queries: inserted
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5 months ago User -is-this-fft- inserted blog post [Tutorial] Online Dynamic
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2:28:54 AM, inserted field deleted false, inserted field hidden false, inserted
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5 months ago User -is-this-fft- inserted blog post A Slight Generalization of
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5 months ago User -is-this-fft- inserted blog post [Tutorial] XOR Convolution
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2:14:52 AM, inserted field deleted false, inserted field hidden false, inserted
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5 months ago User -is-this-fft- inserted blog post A (Somehow) Simple
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5 months ago User -is-this-fft- inserted blog post How to composite (some)
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5 months ago User -is-this-fft- inserted blog post [Tutorial] The residual graph
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6 months ago User Zhtluo inserted blog post All You Need is Randomly Guessing —
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6 months ago User Zhtluo inserted blog post The Reason You are Bad at Codeforces
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8 months ago User pajenegod inserted blog post Shallowest Decomposition Tree by
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8 months ago User pajenegod updated blog post The Ultimate Reroot Template by
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8 months ago User pajenegod updated blog post The Ultimate Reroot Template The
Ultimate Reroot Template by pajenegod: updated field englishDescription
Gives a general and simple to use template for reroot DP on trees, implmented both in Python and C++.,
updated field englishName The Ultimate Reroot Template.
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Catalog
General Advice
* How to come up with solutions?
* How to read problem statements – Um_nik – 6 years ago Collection of
problems with solutions, with an emphasis on reading the problem statement
* How to come up with the solutions: techniques – MikeMirzayanov – 9 years
ago
* Characteristics of the optimal solution, a technique for finding
observations in a problem – Proofy – 3 years ago
* On "is this greedy or DP", forcing and rubber bands – -is-this-fft- – 2
years ago
* How to prove your solutions in Competitive Programming – Everule – 20
months ago
* The Reason You are Bad at Codeforces — You are Not Russian Enough – Zhtluo
– 7 months ago
* All You Need is Randomly Guessing — How to Improve at Codeforces – Zhtluo
– 6 months ago
* How to Solve Questions [Dominater Version] – Dominater069 – 3 weeks ago
* How to practice?
* F.A.Q. (in PM) – Um_nik – 8 years ago
* My opinion on how to practice competitive programming – Radewoosh – 3
years ago
* Self-deception: maybe why you're still grey after practicing every day –
-is-this-fft- – 3 years ago
* How to practice Competitive Programming [Um_nik version] – Um_nik – 3
years ago
* [Tutorial] A way to Practice Competitive Programming : From Rating 1000 to
2400+ – E869120 – 5 years ago
* [Tutorial] How to learn better, and what most people don't get about
learning – nor – 20 months ago
* Pro Tips - get them while they are free – Um_nik – 18 months ago
* How to Effectively Practice CP + Problem Solving Guide – SuperJ6 – 16
months ago A detailed guide on how to practice with reasoning behind
methodology. Also includes advice on approaching and reflecting on
problems.
* How to ask for help?
* How to ask for help in PM – -is-this-fft- – 4 years ago
* Asking for help FAQ – Errichto – 6 years ago
* What not to say when you are accused of cheating – ACGN – 17 months ago
* How to use Codeforces [GUIDE] – SlavicG – 3 years ago
* [Tutorial] The command line: how to read input from file without #ifdef and
much more – -is-this-fft- – 2 years ago
* After a Round FAQ – djm03178 – 2 years ago
Algorithms
* General General discussions that cannot be attributed to a specific topic
* The Ultimate Topic List (with Resources, Problems and Templates) –
YouKn0wWho – 3 years ago
* General ideas – adamant – 8 years ago
* A bit more of general ideas – adamant – 2 years ago
* [Tutorial] Collection of little techniques – -is-this-fft- – 3 years ago
* Binary and Ternary Searches
* EDU: Binary Search – pashka – 4 years ago
* [Tutorial] Binary search and other "halving" methods – nor – 3 years ago
* Bin search and relative error – Um_nik – 8 years ago
* Multi-dimensional ternary search – adamant – 3 years ago
* Parallel Binary Search [tutorial] – himanshujaju – 8 years ago
* An alternative and very interesting approach on binary search – Pankin – 4
years ago
* Binary Lifting, No Memory Wasted – Urbanowicz – 5 years ago Binary lifting
with O(n) memory
* Constructive Algorithms
* Tips on Constructive Algorithms – ReaLNero – 4 years ago
* Data Structures
* Fenwick Tree BIT
* [Tutorial] Searching Binary Indexed Tree in O(log(N)) using Binary
Lifting – sdnr1 – 6 years ago
* [Tutorial] Path sum queries on a tree using a Fenwick tree –
dolphingarlic – 4 years ago
* [Tutorial] A Bit of Math, Historic Sum, and Range Add Range Sum Binary
Indexed Tree (Fenwick Tree) – FHVirus – 3 years ago
* Segment Tree
* EDU: Segment Tree, part 1 – pashka – 4 years ago
* Algorithm Gym :: Everything About Segment Trees – PrinceOfPersia – 10
years ago
* Efficient and easy segment trees – Al.Cash – 9 years ago
* crazySegmentTree: Segment Tree implementation with 5x faster queries
than bottom-up tree – purplesyringa – 3 years ago
* Compressed segment trees and merging sets in O(N logU) – bicsi – 4
years ago
* A simple introduction to "Segment tree beats" – jiry_2 – 7 years ago
* Video: Segment Tree Beats – peltorator – 3 years ago
* [Tutorial] Li Chao Tree Extended – rama_pang – 4 years ago
* [Tutorial] Li Chao Tree Extended 2 – tibinyte – 3 months ago
* using merging segment tree to solve problems about sorted list – TLE –
8 years ago
* [Tutorial] XOR Segment Tree – PurpleCrayon – 2 years ago
* Push-Free Segment Tree – nikgaevoy – 19 months ago
* A Slight Generalization of Push-Free Segment Trees – WLZ – 8 months ago
* Binary Search Trees Cartesian trees, AVL-trees, etc
* Algorithms Thread 9: Treaps (+ Gym Contest!) – SecondThread – 4 years
ago
* [Tutorial] Splay Tree: One Tree to Rule Them All – Zhtluo – 23 months
ago
* "Merging treaps" -- or how to merge sorted sets in good complexity... –
bicsi – 23 months ago
* [Tutorial] Cartesian tree and some related problems – tibinyte – 19
months ago
* Connectivity Queries
* Disjoint Set Union DSU
* EDU: DSU – Aksenov239 – 4 years ago
* [Tutorial] Proving the inverse Ackermann complexity of Union-Find –
-is-this-fft- – 3 years ago
* Link-Cut Trees
* Link-cut tree tutorial – ramchandra – 4 years ago
* Maintain subtree information using link/cut trees – ouuan – 5 years
ago
* [Tutorial] Subtree lazy propagation on the link-cut tree – QCFium –
4 years ago
* Link Cut Tree implementation – bicsi – 4 years ago
* [Tutorial] Online Dynamic Connectivity – ko_osaga – 5 months ago
* Persistence
* AlgorithmsThread 5: Persistent Data Structures – SecondThread – 4 years
ago
* Algorithm Gym :: Data structures – PrinceOfPersia – 10 years ago
* [Tutorial] Supporting Queue-like Undoing on DS – Noam527 – 4 years ago
* Video about Disjoint Sparse Table or how to answer all queries in constant
time – peltorator – 4 years ago
* On Multidimensional Range Queries – Laakeri – 5 years ago Proof (assuming
ETH) of the nonexistence of certain data structures
* [Tutorial] A powerful representation of integer sets – brunomont – 4 years
ago
* [Tutorial] Kinetic Tournament (Used in FBHC Round 2) – ekzhang – 4 years
ago
* Tutorial on Permutation Tree (析合树） – errorgorn – 4 years ago
* Introduction to New Data Structure: Wavelet Trees – rachitiitr – 7 years
ago
* [Tutorial] Sparse table – AlexLuchianov – 2 years ago
* Submask range queries – adamant – 2 years ago O(2^{n/2}) for masks of
length n
* A slightly alternative approach for implementation of optimal LCA –
monsoon – 5 years ago
* [Tutorial] Supporting Priority-Queue-like Undoing on DS – Monogon – 20
months ago
* [Tutorial] On Range LIS Queries, Part 1 – ko_osaga – 20 months ago
* [Tutorial] On Range LIS Queries, Part 2 – ko_osaga – 20 months ago
* [Tutorial] Minimum Deque – k1r1t0 – 10 months ago
* “Log Decomposition”, a technique to insert random elements into sorted
data structures – ismail-but-noob – 8 months ago
* [Tutorial] The sparse set data structure – Redpo – 6 months ago
* Divide-and-conquer
* Dynamic connectivity problem – adamant – 10 years ago
* Divide and conquer. Dynamic connectivity offline and DP optimization.
Divide and conquer by queries. – Wind_Eagle – 2 years ago
* [Tutorial] Divide and Conquer Offline Query — A Niche Way to solve Static
Range Query – steveonalex – 13 months ago
* The Akra-Bazzi theorem — a generalization of the master theorem for
recurrences – nor – 9 months ago
* Dynamic Programming DP
* [Tutorial] Non-trivial DP Tricks and Techniques – zscoder – 8 years ago
* Slope trick explained – Kuroni – 4 years ago
* An Introduction to Plug DP – 4fecta – 3 years ago DP on Broken Profile
* Dynamic Programming Optimizations – indy256 – 11 years ago
* SOS Dynamic Programming [Tutorial] – usaxena95 – 8 years ago
* Incredibly beautiful DP optimization from N^3 to N log^2 N – linkret – 8
years ago
* Theoretical grounds of lambda optimization – adamant – 3 years ago Aliens
Trick
* [Tutorial] Knapsack, Subset Sum and the (max,+) Convolution – errorgorn –
3 years ago
* [Tutorial]Using Segment Trees to solve Dynamic Programming problems –
AlexLuchianov – 2 years ago
* 1D1D-optimization (1D1D-optimization) – seiko.iwasawa – 3 years ago
* An interesting way to solve 739E – krismaz – 8 years ago random-shuffle
sqrt dp optimization
* SMAWK algorithm as an alternative for D&C optimization – ko_osaga – 21
month(s) ago
* Geometry
* [Tutorial] Voronoi Diagram and Delaunay Triangulation in O(n log n) with
Fortune's Algorithm – Monogon – 4 years ago
* O(n) algorithm for finding largest triangle in a convex is wrong? –
u0qyz1234 – 7 years ago
* Efficient 3D Convex Hull Tutorial – Monogon – 4 years ago
* Dynamic convex hull implementation – dragonslayerintraining – 4 years ago
* Geometry: Polygon algorithms – Al.Cash – 8 years ago
* Half-plane intersection (Blogewoosh #5 (with images from now)) – Radewoosh
– 6 years ago
* Quaternion algebra and geometry – adamant – 8 years ago
* Easy geometry using std::complex – Hikari9 – 9 years ago
* Geometry: 2D points and lines [Tutorial] – Al.Cash – 8 years ago
* [Tutorial] Solving Interval Problems with Geometry – Monogon – 3 years ago
* AlgorithmsThread Episode 6: Convex Hull Tricks – SecondThread – 4 years
ago
* Visualization tool for 2D problems (C++) – kalinov – 5 years ago
* Some rotational invariants in geometry – adamant – 3 years ago
* Easy online point location algorithm – qwerty787788 – 23 months ago
* Tiny Dynamic Convex Hull Implementation – brunomont – 19 months ago
* Pythagorean triples and Pell's equations – adamant – 16 months ago
* [Tutorial] Rotating calipers technique and its applications – asdasdqwer –
9 days ago
* Games
* A blog on the Sprague-Grundy Theorem – sirknightingfail – 6 years ago
* The Intuition Behind NIM and Grundy Numbers in Combinatorial Game Theory –
Shisuko – 6 years ago
* [Tutorial] Slight Generalization of Grundy Numbers – emorgan – 4 years ago
Transfinite Grundy numbers
* Nimbers and Sprague-Grundy theorem – adamant – 2 years ago
* Graphs
* Depth-first Search DFS
* [Tutorial] The DFS tree and its applications: how I found out I really
didn't understand bridges – -is-this-fft- – 5 years ago
* My own algorithm — offline incremental strongly connected components in
O(m*log(m)) – Radewoosh – 3 years ago
* [Tutorial] Directed DFS trees (and the Tarjan algorithm for Strongly
Connected Components) – de_sousa – 2 months ago
* Shortest Paths
* 0-1 BFS [Tutorial] – himanshujaju – 9 years ago
*
* [Tutorial] k shortest paths and Eppstein's algorithm – meooow – 2 years
ago
* Rethink the Dijkstra algorithm -- Let's go deeper – CristianoPenaldo –
23 months ago
* [Tutorial] The Floyd-Warshall algorithm and its generalizations – nor –
15 months ago
* Trees
* Algorithms Thread 8: Tree Basics (+ Gym Contest) – SecondThread – 4
years ago Finding diameters, binary lifting and flattening
* A list of important concepts in Tree-based Problems – dvdg6566 – 4
years ago
* Hybrid Tutorial #-1: Heavy-Light Decomposition – galen_colin – 4 years
ago
* Heavy-light decompositon — it can be simple! – Vladyslav – 10 years ago
* Easiest HLD with subtree queries – adamant – 7 years ago
* [Tutorial] Sack (dsu on tree) – Arpa – 8 years ago Small-to-large
merging
* Hybrid Tutorial #-2: Centroid Decomposition – galen_colin – 4 years ago
*
* Heavy-light decomposition implementation – Al.Cash – 9 years ago
* [Tutorial] Path sum queries on a tree using a Fenwick tree –
dolphingarlic – 4 years ago
* Bridge Trees [Tutorial] – aryan12 – 3 years ago
* Line tree (Path max queries on a tree in O(1)) – neal – 5 years ago
Description is in Kaban-5 comment
* [Tutorial] Binary lifting – AlexLuchianov – 3 years ago
* [Tutorial] Tree Isomorphism CSES – Olympia – 3 years ago
* [Tutorial] Diameter of a tree and its applications – TheScrasse – 2
years ago
* [Tutorial] Fully Dynamic Trees Supporting Path/Subtree Aggregates and
Lazy Path/Subtree Updates – smax – 2 years ago
* [Tutorial] Theoretically Faster HLD and Centroid Decomposition –
errorgorn – 2 years ago
* [Insight] Number of Topological Orderings of a Directed Tree –
Osama_Alkhodairy – 4 years ago
* [Idea] Using HLD to reduce memory – maomao90 – 19 months ago
* Optimal 2/3 halving in interactive tree problems – maomao90 – 12 months
ago
* The Ultimate Reroot Template – pajenegod – 8 months ago For C++ and
Python
* Shallowest Decomposition Tree – pajenegod – 8 months ago
* Matchings
* [Tutorial] Blossom Algorithm for General Matching in O(n^3) – Monogon –
3 years ago
*
* Randomized general matching with Tutte matrix – adamant – 3 years ago
* [Tutorial] Hungarian algorithm in Õ(mn) or O(n^3) – -is-this-fft- – 5
months ago
* Flows
* [Tutorial, Flows] Project Selection Problem – AlexLuchianov – 2 years
ago
* [Tutorial] My way of understanding Dinitz's ("Dinic's") algorithm –
-is-this-fft- – 2 years ago
* [Tutorial] Minimum cost (maximum) flow – -is-this-fft- – 2 years ago
* [Tutorial] More about minimum cost flows: potentials and Dinitz –
-is-this-fft- – 2 years ago
* [Tutorial] Network simplex – brunovsky – 3 years ago
* Kőnig's and Hall's theorems through minimum cut in bipartite graphs –
adamant – 2 years ago
* [Tutorial] Simulating Cost Flow – smax – 14 months ago
* Implementing Dinitz on bipartite graphs – adamant – 14 months ago
* [Tutorial] The residual graph and working with the set of all minimum
cuts – -is-this-fft- – 5 months ago
* Heuristic algorithm for Hamiltonian path in directed graphs – Rewinding –
3 years ago
* [Tutorial] Graph Potentials, Johnson's Algorithm, and Min Cost Max Flow –
Monogon – 3 years ago
* [Tutorial] Boruvka's Algorithm – RockyB – 4 years ago
* Algorithm Gym :: Graph Algorithms – PrinceOfPersia – 10 years ago
* Traversing the complement graph in linear/near-linear time in multiple
ways – nor – 3 years ago
* Story about edge coloring of graph – ko_osaga – 4 years ago Vizing's
Theorem
* Merging Queries Trick – SlavicG – 3 years ago
* A Brief Inquiry into Online Connectivity – ko_osaga – 11 months ago
* Greedy Algorithms
* [Tutorial] Matroid intersection in simple words – ATSTNG – 5 years ago
* [Tutorial] Greedoids: a formal way to look at families of
greedily-solvable problems – nor – 20 months ago
* Hashing
* Blowing up unordered_map, and how to stop getting hacked on it – neal – 6
years ago
* [Tutorial] Rolling hash and 8 interesting problems [Editorial] – dmkz – 6
years ago
* On the mathematics behind rolling hashes and anti-hash tests – dacin21 – 6
years ago
* Analysis of polynomial hashing – purplesyringa – 3 years ago
* Anti-hash test. – Zlobober – 12 years ago
* Kapun's algorithm – purplesyringa – 3 years ago
* [Tutorial] Hacking a weak hash – TheScrasse – 19 months ago
* A tool for hacking rolling hashes with fixed modulos and bases – Sugar_fan
– 4 months ago
* Mathematics
* Bitwise Operations
* Bitwise operations for beginners – Errichto – 5 years ago
* Bitwise operations 2 — popcount & bitsets – Errichto – 5 years ago
* A Beautiful Technique for Some XOR Related Problems – DrSwad – 5 years
ago Gaussian elimination, a.k.a xor basis
* XOR basis without linear algebra – Everule – 3 years ago
* Number Theory
* [Tutorial] Generalized Möbius Inversion on Posets – nor – 3 years ago
* [Tutorial] Catalan Numbers and Catalan Convolution – Dardy – 4 years
ago
* Short modular inverse – _h_ – 9 years ago
* Counting Divisors of a Number in $O(N^{\frac{1}{3}})$ [tutorial] –
himanshujaju – 9 years ago
* Counting primes in $\tilde{{\cal O}}(n^{2/3}\,\,)$ – Maksim1744 – 3
years ago
* Finding minimum residue of a linear function in O(log M) time –
mango_lassi – 3 years ago
* On the Min25 sieve and extensions / SPOJ ASSIEVE – box – 3 years ago
* [Tutorial] Math note — Möbius inversion – Nisiyama_Suzune – 7 years ago
* [Tutorial] Math note — Dirichlet convolution – Nisiyama_Suzune – 7
years ago
* Essential Elementary Number Theory (Essentials of Elementary Number
Theory) – Everule – 3 years ago GCD, Bezout's Theorem, Extended CRT,
Mobius and other multiplicative functions, Primitive roots and
Probabilistic prime tests
* A slightly faster algorithm for finding square root modulo an odd prime
– hly1204 – 3 years ago
* On continued fractions. Part 3: In competitive programming – adamant –
2 years ago
* p-adic exponent or why there is a primitive root modulo powers of prime
numbers (except 2) – adamant – 2 years ago
* [Tutorial] Berlakamp's Algorithm for Polynomial Factorization in a
Field (1698G buffed) – errorgorn – 2 years ago
* [Tutorial] Euler's phi function, its properties, and how to compute it
– kamilszymczak1 – 2 years ago
* Implicit Prime Factorisation – Everule – 23 months ago
* Lucas Theorem (Lucas Theorem is not an equation, it's an operation!) –
Everule – 12 months ago
* Integer solutions to x² + y² = z – adamant – 16 months ago
* Division-less Euclid's algorithm – orz – 9 months ago
* Probability Theory
* Sums and Expected Value — part 1 – Errichto – 6 years ago
* Sums and Expected Value — part 2 – Errichto – 6 years ago
* [Tutorial] Expected number of coin flips required to achieve a given
string – gabrielwu – 3 years ago
* Intuition and application of Martingales (Probability 101, the
intuition behind martingales and solving problems with them) – nor – 21
month(s) ago Applying results of Martingales to prove a wide variety of
claims.
* Сombinatorics
* [Tutorial] Inclusion-Exclusion Principle – Roundgod – 6 years ago
* Young Tableaus and the Hook Length Formula – mango_lassi – 3 years ago
* [Tutorial] Burnside's lemma (with example) – TwoFx – 6 years ago
* [Tutorial] Invariants and Monovariants – TooNewbie – 7 years ago
* Catalan Numbers and Generating Uniform Balanced Bracket Sequences –
errorgorn – 2 years ago
* An intuition and simpler proof for Kirchoff's tree theorem – Everule –
2 years ago
* Lattice paths and Lindström–Gessel–Viennot lemma – miaowtin – 23 months
ago
* [Tutorial] From Burnside to Polya: A Short Introduction to Group Theory
([Tutorial] From Burnside to Polya: A Short Introduction to Group
Theory) – Zhtluo – 14 months ago
* MacMahon's master theorem – adamant – 9 months ago
* Linear Algebra
* A Beautiful Technique for Some XOR Related Problems – DrSwad – 5 years
ago Gaussian elimination
* Linear Basis (Xor Basis Extended) – errorgorn – 3 years ago
Generalization of Gaussian elimination to integers modulo a composite
number (and beyond).
* 2 Special cases of Gaussian [Tutorial] – MazzForces – 6 years ago
Markov Chains (for Cyclic Expected Values) and the "XOR basis"
technique
* A (Somehow) Simple (Randomized) Algorithm for Frobenius Form of a
Matrix – MyBotDear – 8 months ago
* Permutations
* [Tutorial] A comprehensive guide to permutations for beginners – nor –
20 months ago
* Tutorial on Permutation Tree (析合树） – errorgorn – 4 years ago
* Permutation group basis construction (Schreier–Sims algorithm) –
adamant – 20 months ago
* Polynomials, Series and Recurrences
* Generating Functions General theory; algorithms are under FFT
* [Tutorial] Generating Functions in Competitive Programming (Part 1)
– zscoder – 4 years ago
* [Tutorial] Generating Functions in Competitive Programming (Part 2)
– zscoder – 4 years ago
* A problem collection of ODE and differential technique – jqdai0815 –
4 years ago
* Prefix Sum Polynomial – Lain – 3 years ago
* Combinatorial species: An intuition behind generating functions –
adamant – 2 years ago Simple way to construct generating functions
and interpret operations on them.
* Unlabeling combinatorial species (cycle index series) – adamant – 20
months ago Finding OGFs for unlabeled species composition
* Moment-generating functions, inversions and q-analogs – adamant – 3
years ago
* OGFs, EGFs, differentiation and Taylor shifts – adamant – 3 years
ago
* Fast polynomial composition – adamant – 2 years ago Given A(x) and
B(x), compute first n coefficients of A(B(x)).
* Lagrange inversion theorem – adamant – 2 years ago Given x = f(y),
find coefficients of g(x) such that y = g(x).
* Partitions and pentagonal number theorem – adamant – 2 years ago
Explicit formula for (1-x)(1-x^2)(1-x^3)... and applications
* Arrow product: How to enumerate directed graphs – adamant – 17
months ago
* Shift of polynomial sampling points – adamant – 17 months ago
* Unexpected application of cosines – adamant – 18 months ago
* Solving the "simple math problem" with generating functions –
adamant – 15 months ago
* Shift of polynomial sampling points – adamant – 17 months ago
* FFT and Similar Transformations Algorithms for operating on polynomials
* [Tutorial] FFT – -is-this-fft- – 20 months ago
* Tutorial on FFT/NTT — The tough made simple. ( Part 1 ) – sidhant –
9 years ago
* Notes on FFT / NTT, and the "ultimate" NTT with modulus > 9 * 10^18
– Spheniscine – 4 years ago
* On Fast Fourier Transform – adamant – 7 years ago
* Operations on Formal Power Series – rng_58 – 7 years ago
* Operations on polynomials (on cp-algorithms) – adamant – 6 years ago
Fast polynomial division, evaluation, interpolation.
* [Tutorial] Generalized Chirp Z-Transform – box – 4 years ago
* Discrete Fourier Transform eigenvalues – adamant – 3 years ago
* A simple way to understand the transposed algo of multi-eval (A
simple way to understand the transposed algo of multi-eval) –
hly1204 – 3 years ago
* An unexpected D&C with FFT – Um_nik – 2 years ago
* Tutorial: A simple O(n log n) polynomial multiplication algorithm
(Tutorial: A simple O(n log n) polynomial multiplication algorithm)
– pajenegod – 14 months ago
* Introducing the imaginary cyclic convolution, speeding up
convolution by a factor of 2 – pajenegod – 2 years ago
* Fast convolution for 64-bit integers – quasisphere – 8 years ago
* CDQ convolution (online FFT) generalization with Newton method –
adamant – 20 months ago
* How to composite (some) polynomials faster? – Elegia – 7 months ago
* On implementing O(nlog(n)^2) algorithm of FPS composition – hly1204
– 6 months ago
* Montgomery/Barret reduction and NTT [Performance optimization] –
alexvim – 4 months ago
* Bitwise Convolutions Xor-, or- and subset convolution, "set power
series"
* Generalized FWHT: How I realized I did not understand FWHT –
errorgorn – 3 years ago
* Tutorial on Zeta Transform, Mobius Transform and Subset Sum
Convolution – sidhant – 5 years ago
* Fast Walsh Hadamard Transforms and it's inner workings – upobir – 5
years ago
* Subset convolution interpretation – adamant – 3 years ago
* Optimal Algorithm on Polynomial Composite Set Power Series – Elegia
– 3 years ago
* OR Convolution for Common People – ko_osaga – 17 months ago
* [Tutorial] GCD Convolution – szaranczuk – 19 months ago
* [Tutorial] Zeta, Mobius Transform to AND, OR, GCD Convolution –
jinhan814 – 13 months ago
* Some SOS DP Insights (Some SOS DP Insights) – maxwellzen – 2 years
ago An interesting interpretation of SOS DP (also known as zeta
transform and under a few other names) as a multidimensional
instance of prefix sums.
* [Tutorial] XOR Convolution without math – k1r1t0 – 6 months ago
* Linear Recurrences
* Matrix Exponentiation tutorial + training contest – Errichto – 4
years ago
* On linear recurrences and the math behind them – adamant – 3 years
ago
* Recovering a linear recurrence with the extended Euclidean algorithm
– adamant – 2 years ago
* Half-GCD algorithm – adamant – 2 years ago Compute polynomial GCD or
recover minimum recurrence in O(n log^2 n)
* Linear Recurrence and Berlekamp-Massey Algorithm – TLE – 6 years ago
* [Tutorial] Berlekamp-Massey – smax – 3 years ago
* [Math note] On the relationship between gf and me – -is-this-fft- –
3 years ago Correspondence between generating function and matrix
exponentiation for solving linear recurrences
* [Tutorial] Solving Linear Recurrences with various methods,
Including O(N logN logK) using FFT – demoralizer – 3 years ago
Computing f(k) where f(k) is a linear recurrence of N terms in O(N *
log(N) * log(k))
* Hadamard product and binomial convolution of linear recurrences –
adamant – 2 years ago
* [Tutorial] An elementary way of solving recurrences – nor – 8 months
ago
* Lagrange interpolation and partial fraction decomposition – adamant – 3
years ago
* Computing n! modulo pᵏ for small p – adamant – 16 months ago
* Calculating Series Sums with Binary Exponentiation – UnexpectedValue –
10 months ago
* Snapshot of finite calculus and using it to solve a 3000 rated problem
– WeakestTopology – 2 days ago
* Optimization Anything related to mathematical optimization
* Multi-dimensional ternary search – adamant – 3 years ago
* Theoretical grounds of lambda optimization – adamant – 3 years ago
Aliens Trick
* Duality in linear programming. Part 1 — definition and construction –
adamant – 2 years ago
* Duality in linear programming. Part 2 — in competitive programming –
adamant – 2 years ago
* Abstract nonsense Abstract algebra and friends
* Permutation group basis construction (Schreier–Sims algorithm) –
adamant – 20 months ago
* Associativity and general identity testing – adamant – 3 years ago
* [Tutorial] 2-SAT – arujbansal – 3 years ago
* 2-SAT Tutorial – HosseinYousefi – 10 years ago
* An interesting algebraic construction – box – 3 years ago
* [Tutorial] Floors, ceilings and inequalities for beginners (with some
programming tips) – nor – 18 months ago
* Non-exact and Randomized Algorithms
* [Tutorial] Simulated Annealing in Competitive Programming – PurpleCrayon –
3 years ago
* Randomized algorithms lecture, part 1 & 2 – Errichto – 5 years ago
* Blogewoosh #1 – Radewoosh – 6 years ago
* Blogewoosh #6 – Radewoosh – 6 years ago
* On the Number of Runs at the Monte-Carlo Method – rotavirus – 4 years ago
* Randomized general matching with Tutte matrix – adamant – 3 years ago
* How randomized solutions can be hacked, and how to make your solution
unhackable – neal – 6 years ago
* Sortings
* Lecture #3 — Exchange arguments (sorting with dp) – Errichto – 6 years ago
* Square Root Techniques SQRT decomposition, Mo's algorithm, etc
* [Tutorial] Square Root Techniques – Errichto – 3 years ago
* An alternative sorting order for Mo's algorithm – gepardo – 6 years ago
* Mo's Algorithm on Trees [Tutorial] – animeshf – 9 years ago
* Sqrt-tree: answering queries in O(1) with O(NloglogN) preprocessing. –
gepardo – 7 years ago
* [Tutorial] Square root decomposition and applications – box – 4 years ago
* Unknown Data Structure — (Sqrt Fragmented Tree) – cjtoribio – 8 years ago
* [Tutorial] Subset Sum Square Root Optimisation – arujbansal – 3 years ago
* Strings
* [Tutorial] Dynamic Suffix Arrays – brunomont – 3 years ago
* On suffix automaton (and tree) – adamant – 9 years ago
* Aho-Corasick algorithm. Construction – adamant – 10 years ago
* A short guide to suffix automata – quasisphere – 9 years ago
* Palindromic tree: behind the scenes – adamant – 10 years ago
* A bit more about palindromes – adamant – 9 years ago You're given a
string, split it into the minimum number of palindromes.
* The history of some recurring problem – adamant – 6 years ago You're given
a string s and queries: how many distinct substrings does sl...sr have?
* Suffix tree. Ukkonen's algorithm – adamant – 10 years ago
* [Tutorial] Expected number of coin flips required to achieve a given
string – gabrielwu – 3 years ago
* [Tutorial] Dictionary of Basic Factors — O(1) String Matching – Leonardo16
– 3 years ago
* Z Algorithm – paladin8 – 13 years ago
* [Tutorial] On Variations of String Matching – brunomont – 20 months ago
* Random notes on Lyndon decomposition – ko_osaga – 2 years ago
* Sweeping Line
* How to sweep like a Sir – DanAlex – 9 years ago
* [Tutorial] Finding inclusion hierarchy among circles — An implementation
of a sweep-line algorithm – Arpa – 3 years ago
* Two Pointers
* EDU: Two Pointers Method – pashka – 4 years ago
Programming Languages
* C++
* C++ Tricks – HosseinYousefi – 10 years ago
* Catching silly mistakes with GCC – andreyv – 10 years ago
* Don't use rand(): a guide to random number generators in C++ – neal – 6
years ago
* [Tutorial] GCC Optimization Pragmas – nor – 3 years ago
* C++ tips and tricks – Golovanov399 – 5 years ago
*
* Performance tip : using std::deque as a memory cache – mouse_wireless – 6
years ago
* C++ STL: Policy based data structures – adamant – 10 years ago Like
std::set, but with O(log n) methods to get k-th element and count elements
that are less the given one.
* Implicit cartesian tree in GNU C++ STL. – Perlik – 11 years ago Like
std::string, but can move substrings around in O(log n).
* A way to use C++ iostream for large input (gcc only) – yak_ex – 14 years
ago
* Tutorial on SIMD vectorisation to speed up brute force – maomao90 – 3
years ago
* Generic data structure templates via C++ mixins – clam – 3 years ago
* Explanation to weird/strange floating point behaviour in C++ – pajenegod –
4 years ago Why you sometimes get WA with 64-bit but not 32-bit compiler
* How NOT to use macros – AlexLuchianov – 3 years ago
* How to get actual 64 bit bitsets on Codeforces [Not Recommended] [Don't do
this at your job] – Chilli – 4 years ago
* [Tutorial] Writing C++ like Python: tricks Python doesn't want you to know
– nor – 20 months ago
* Template Metaprogramming in C++ Part 1 / Infinity – Everule – 19 months
ago
* [Tutorial] Quick start in solving problems on GPU + CPU – dmkz – 15 months
ago
* [Tutorial] On lambdas, C++ and otherwise: the what, the why, and the how –
nor – 10 months ago
* [C++] Avoiding temporaries — generalizing i++ using std::exchange – nor –
10 months ago
* [Bugged] Dynamic Bitsets in GCC – bitset – 4 months ago
* C++ STL: Order of magnitude faster hash tables with Policy Based Data
Structures – Chilli – 6 years ago
* D
* The D programming language in competitive programming – Gassa – 6 years
ago
Meta Posts that are important for competitive programming as a whole
* Tools
* CF-Predictor — Know your rating changes! – WasylF – 8 years ago
* Multiple rating graph with other accounts – yak_ex – 13 years ago
*
* Have you already seen the history of ratings on clist? – aropan – 4 years
ago Rating aggregation from different competitive programming sites.
* Codeforces Extensions – MohamedAboOkail – 4 years ago
* Gym Finder – NightRage – 3 years ago
* Userscript: table view in Catalog – -is-this-fft- – 2 years ago
*
* Finally, semantic search for competitive programming problems – TLE – 10
months ago
* Libraries
* AtCoder Library – rng_58 – 4 years ago A professionally-developed
competitive programming library.
* New online judge: Library-Checker! – yosupo – 4 years ago
* (The Ultimate) Code Library – YouKn0wWho – 3 years ago
* Announcements Resources that help keeping track of upcoming contests.
* pe in 30 – Golovanov399 – 3 years ago Telegram channel with 30-minutes
announcements for new problems at projecteuler.
* Resource clist.x10.mx moved to clist.by – aropan – 13 years ago Contest
calendar and more
Problem and Contest Preparation
* Testlib and Polygon
* Briefly about testlib.h – MikeMirzayanov – 9 years ago
* Generators with testlib.h – MikeMirzayanov – 9 years ago
* Validators with testlib.h – I_love_Hoang_Yen – 9 years ago
* Checkers with testlib.h – Zlobober – 9 years ago
* Interactors with testlib.h – PrinceOfPersia – 9 years ago
*
* 10 Reasons to Prepare Problems in Polygon – MikeMirzayanov – 10 years ago
* [Tutorial] Polygon.Codeforces Tutorial — A Guide to Problem Preparation
[Part 1] – darkkcyan – 2 years ago
* Polygon Updates (Fall-Winter 2014) – Avalanche – 10 years ago
* Testlib and Polygon Updates (June, 2015) – fcspartakm – 9 years ago
* Testlib and Polygon Updates [July, 2018] – MikeMirzayanov – 6 years ago
* Polygon updates (June-October 2019) – geranazavr555 – 5 years ago
* Polygon Updates (June — August 2021) – unreal.eugene – 3 years ago
* Testlib: Opts — parsing command line options – MikeMirzayanov – 5 years
ago
* Testlib: tests + CI – MikeMirzayanov – 2 years ago
* Problemsetting Interviews with problemsetters, how to come up with problem
ideas etc.
* How to come up with problem ideas – Lewin – 5 years ago
* On problemsetting – antontrygubO_o – 5 years ago
* On problemsetting 2 – antontrygubO_o – 5 years ago
* Way of problemsetter – Sammarize – 10 years ago
* What is it like to be a problem writer? – Nickolas – 13 years ago
* Problemsetter's Memoir – Nickolas – 10 years ago
* About Problemsetting (for AtCoder and Codeforces) – dario2994 – 4 years
ago
* [Problemsetting] How to write editorials for a contest – okwedook – 19
months ago
* Insights from testing and preparing contests, and why problemsetting
trends need to change – nor – 20 months ago
Interviews
* EPISODE 1: Interview with Um_nik – Agnimandur – 18 months ago
* 700 contests. ruban's interview – pani.natalia – 3 years ago
* How to be red: Arpa – pani.natalia – 4 years ago
* deltixlab’s interview: Deltix rounds back story – pani.natalia – 3 years ago
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ask for help? Algorithms General Binary and Ternary Searches Constructive
Algorithms Data Structures Fenwick Tree Segment Tree Binary Search Trees
Connectivity Queries Disjoint Set Union Link-Cut Trees Persistence
Divide-and-conquer Dynamic Programming Geometry Games Graphs Depth-first Search
Shortest Paths Trees Matchings Flows Greedy Algorithms Hashing Mathematics
Bitwise Operations Number Theory Probability Theory Сombinatorics Linear Algebra
Permutations Polynomials, Series and Recurrences Generating Functions FFT and
Similar Transformations Bitwise Convolutions Linear Recurrences Optimization
Abstract nonsense Non-exact and Randomized Algorithms Sortings Square Root
Techniques Strings Sweeping Line Two Pointers Programming Languages C++ D Meta
Tools Libraries Announcements Problem and Contest Preparation Testlib and
Polygon Problemsetting Interviews
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