Catalog - Codeforces

→ History

6 weeks ago User peltorator updated blog post OpenCup News by Um_nik: updated field hidden ~~fals~~true.

2 months ago User Benq updated blog post Random notes on Lyndon decomposition Random notes on Lyndon decomposition by ko_osaga: updated field englishName ~~Random notes on Lyndon decomposition~~.

2 months ago User Benq inserted blog post Random notes on Lyndon decomposition Random notes on Lyndon decomposition by ko_osaga: inserted field blogEntryId 106725, inserted field catalogFolder Strings, inserted field creationTime Jan 31, 2023, 10:13:32 PM, inserted field deleted false, inserted field englishName Random notes on Lyndon decomposition, inserted field hidden false, inserted field position 1300.

2 months ago User adamant updated blog post Unlabeling combinatorial species (cycle index series) by adamant: updated field englishDescription Finding OGFs for unlabeled species composition.

2 months ago User adamant inserted blog post Unlabeling combinatorial species (cycle index series) by adamant: inserted field blogEntryId 111889, inserted field catalogFolder Generating Functions, inserted field creationTime Jan 27, 2023, 5:53:28 PM, inserted field deleted false, inserted field hidden false, inserted field position 750.

2 months ago User -is-this-fft- inserted blog post How to prove your solutions in Competitive Programming by Everule: inserted field blogEntryId 111849, inserted field catalogFolder How to come up with solutions?, inserted field creationTime Jan 25, 2023, 10:52:42 PM, inserted field deleted false, inserted field hidden false, inserted field position 900.

2 months ago User -is-this-fft- inserted blog post [Tutorial] On Range LIS Queries, Part 2 by ko_osaga: inserted field blogEntryId 111807, inserted field catalogFolder Data Structures, inserted field creationTime Jan 25, 2023, 9:31:11 AM, inserted field deleted false, inserted field hidden false, inserted field position 1500.

2 months ago User -is-this-fft- inserted blog post [Tutorial] On Range LIS Queries, Part 1 by ko_osaga: inserted field blogEntryId 111625, inserted field catalogFolder Data Structures, inserted field creationTime Jan 20, 2023, 6:25:07 AM, inserted field deleted false, inserted field hidden false, inserted field position 1400.

2 months ago User -is-this-fft- inserted blog post [Tutorial] On Variations of String Matching by brunomont: inserted field blogEntryId 111380, inserted field catalogFolder Strings, inserted field creationTime Jan 14, 2023, 2:16:51 PM, inserted field deleted false, inserted field hidden false, inserted field position 1200.

2 months ago User -is-this-fft- inserted blog post Permutation group basis construction (Schreier–Sims algorithm) by adamant: inserted field blogEntryId 111290, inserted field catalogFolder Permutations, inserted field creationTime Jan 14, 2023, 2:16:00 PM, inserted field deleted false, inserted field hidden false, inserted field position 300.

2 months ago User -is-this-fft- inserted blog post Tutorial on Permutation Tree (析合树） by errorgorn: inserted field blogEntryId 78898, inserted field catalogFolder Permutations, inserted field creationTime Jan 14, 2023, 2:15:51 PM, inserted field deleted false, inserted field hidden false, inserted field position 200.

2 months ago User -is-this-fft- inserted blog post [Tutorial] A comprehensive guide to permutations for beginners by nor: inserted field blogEntryId 111187, inserted field catalogFolder Permutations, inserted field creationTime Jan 14, 2023, 2:14:59 PM, inserted field deleted false, inserted field hidden false, inserted field position 100.

2 months ago User -is-this-fft- updated folder Permutations: updated field position 7600.

2 months ago User -is-this-fft- updated folder FFT and Similar Transformations: updated field position 6700.

2 months ago User -is-this-fft- updated folder Permutations: updated field position 8700.

2 months ago User -is-this-fft- updated folder Polynomials, Series and Recurrences: updated field position 7800.

2 months ago User -is-this-fft- updated folder Permutations: updated field position 9800.

2 months ago User -is-this-fft- updated folder Optimization: updated field position 8900.

2 months ago User -is-this-fft- updated folder Permutations: updated field position 10900.

2 months ago User -is-this-fft- updated folder Abstract nonsense: updated field position 91000.

2 months ago User -is-this-fft- inserted folder Permutations: inserted field creationTime Jan 14, 2023, 2:14:17 PM, inserted field deleted false, inserted field englishName Permutations, inserted field hidden false, inserted field parentCatalogFolder Mathematics, inserted field position 1000.

2 months ago User adamant inserted blog post CDQ convolution (online FFT) generalization with Newton method by adamant: inserted field blogEntryId 111399, inserted field catalogFolder FFT and Similar Transformations, inserted field creationTime Jan 14, 2023, 1:21:42 PM, inserted field deleted false, inserted field hidden false, inserted field position 1500.

2 months ago User -is-this-fft- inserted blog post [Tutorial] FFT by -is-this-fft-: inserted field blogEntryId 111371, inserted field catalogFolder FFT and Similar Transformations, inserted field creationTime Jan 13, 2023, 10:50:41 PM, inserted field deleted false, inserted field hidden false, inserted field position -1.

3 months ago User adamant inserted blog post [Tutorial] Writing C++ like Python: tricks Python doesn't want you to know by nor: inserted field blogEntryId 111253, inserted field catalogFolder C++, inserted field creationTime Jan 12, 2023, 7:05:54 AM, inserted field deleted false, inserted field hidden false, inserted field position 1700.

3 months ago User adamant updated folder Abstract nonsense: updated field englishDescription Abstract algebra and friends.

3 months ago User adamant updated blog post Associativity and general identity testing by adamant: updated field catalogFolder ~~Mathematics~~Abstract nonsense.

3 months ago User adamant inserted blog post Permutation group basis construction (Schreier–Sims algorithm) by adamant: inserted field blogEntryId 111290, inserted field catalogFolder Abstract nonsense, inserted field creationTime Jan 12, 2023, 4:23:27 AM, inserted field deleted false, inserted field hidden false, inserted field position 100.

3 months ago User adamant inserted folder Abstract nonsense: inserted field creationTime Jan 12, 2023, 4:23:16 AM, inserted field deleted false, inserted field englishName Abstract nonsense, inserted field hidden false, inserted field parentCatalogFolder Mathematics, inserted field position 900.

3 months ago User adamant inserted blog post How to get actual 64 bit bitsets on Codeforces [Not Recommended] [Don't do this at your job] by Chilli: inserted field blogEntryId 77480, inserted field catalogFolder C++, inserted field creationTime Jan 9, 2023, 2:03:43 PM, inserted field deleted false, inserted field hidden false, inserted field position 1600.

3 months ago User -is-this-fft- inserted blog post [Tutorial] Supporting Priority-Queue-like Undoing on DS by Monogon: inserted field blogEntryId 111117, inserted field catalogFolder Data Structures, inserted field creationTime Jan 9, 2023, 11:59:40 AM, inserted field deleted false, inserted field hidden false, inserted field position 1300.

3 months ago User -is-this-fft- updated folder Data Structures: updated field hidden ~~tru~~false.

3 months ago User -is-this-fft- updated folder Data Structures: updated field hidden ~~fals~~true.

3 months ago User -is-this-fft- inserted blog post SMAWK algorithm as an alternative for D&C optimization by ko_osaga: inserted field blogEntryId 110844, inserted field catalogFolder Dynamic Programming, inserted field creationTime Jan 9, 2023, 11:58:23 AM, inserted field deleted false, inserted field hidden false, inserted field position 1200.

3 months ago User -is-this-fft- inserted blog post [Tutorial] Greedoids: a formal way to look at families of greedily-solvable problems by nor: inserted field blogEntryId 110961, inserted field catalogFolder Greedy Algorithms, inserted field creationTime Jan 9, 2023, 11:57:46 AM, inserted field deleted false, inserted field hidden false, inserted field position 200.

3 months ago User Everule updated blog post Application of Martingales Probability 101, the intuition behind martingales and solving problems with them by nor: updated field englishDescription ~~Using Martingales and the Optional Stopping theorem, in context of Measure Theory and Sigma Algebra~~Applying results of Martingales to prove a wide variety of claims., updated field englishName AIntuition and application of Martingales.

3 months ago User Everule inserted blog post Application of Martingales Probability 101, the intuition behind martingales and solving problems with them by nor: inserted field blogEntryId 110801, inserted field catalogFolder Probability Theory, inserted field creationTime Jan 1, 2023, 3:29:28 PM, inserted field deleted false, inserted field englishDescription Using Martingales and the Optional Stopping theorem, in context of Measure Theory and Sigma Algebra., inserted field englishName Application of Martingales, inserted field hidden false, inserted field position 400.

3 months ago User Everule updated folder Probability Theory: updated field position 4300.

3 months ago User Everule updated folder Сombinatorics: updated field position 3400.

3 months ago User -is-this-fft- inserted blog post "Merging treaps" -- or how to merge sorted sets in good complexity... by bicsi: inserted field blogEntryId 108601, inserted field catalogFolder Binary Search Trees, inserted field creationTime Dec 26, 2022, 9:16:15 PM, inserted field deleted false, inserted field hidden false, inserted field position 800.

4 months ago User ftiasch inserted blog post Fast convolution for 64-bit integers by quasisphere: inserted field blogEntryId 45298, inserted field catalogFolder FFT and Similar Transformations, inserted field creationTime Dec 1, 2022, 6:39:37 AM, inserted field deleted false, inserted field hidden false, inserted field position 1400.

5 months ago User radal inserted blog post A slightly alternative approach for implementation of optimal LCA by monsoon: inserted field blogEntryId 67138, inserted field catalogFolder Data Structures, inserted field creationTime Nov 3, 2022, 2:54:16 PM, inserted field deleted false, inserted field hidden false, inserted field position 1200.

5 months ago User Zhtluo updated blog post [Tutorial] Splay Tree: One Tree to Rule Them All by Zhtluo: updated field position 12700.

5 months ago User Zhtluo updated blog post [Tutorial] Splay Tree: One Tree to Rule Them All by Zhtluo: updated field catalogFolder ~~Data Structur~~Binary Search Trees.

5 months ago User Zhtluo inserted blog post [Tutorial] Splay Tree: One Tree to Rule Them All by Zhtluo: inserted field blogEntryId 108457, inserted field catalogFolder Data Structures, inserted field creationTime Oct 27, 2022, 3:09:38 AM, inserted field deleted false, inserted field hidden false, inserted field position 1200.

5 months ago User dario2994 updated blog post Lattice paths and Lindström–Gessel–Viennot lemma by miaowtin: updated field englishDescription ~~Description of the Lindström–Gessel–Viennot lemma, which allows to compute a signed sum over disjoint paths in a graph.~~.

5 months ago User dario2994 inserted blog post Lattice paths and Lindström–Gessel–Viennot lemma by miaowtin: inserted field blogEntryId 108395, inserted field catalogFolder Сombinatorics, inserted field creationTime Oct 26, 2022, 5:23:44 AM, inserted field deleted false, inserted field englishDescription Description of the Lindström–Gessel–Viennot lemma, which allows to compute a signed sum over disjoint paths in a graph., inserted field hidden false, inserted field position 800.

5 months ago User -is-this-fft- inserted blog post Implicit Prime Factorisation by Everule: inserted field blogEntryId 108053, inserted field catalogFolder Number Theory, inserted field creationTime Oct 16, 2022, 7:03:39 AM, inserted field deleted false, inserted field hidden false, inserted field position 1600.

5 months ago User -is-this-fft- inserted blog post Easy online point location algorithm by qwerty787788: inserted field blogEntryId 107901, inserted field catalogFolder Geometry, inserted field creationTime Oct 14, 2022, 4:14:54 AM, inserted field deleted false, inserted field hidden false, inserted field position 2200.

6 months ago User -is-this-fft- inserted blog post Rethink the Dijkstra algorithm -- Let's go deeper by CristianoPenaldo: inserted field blogEntryId 107810, inserted field catalogFolder Shortest Paths, inserted field creationTime Oct 11, 2022, 7:30:42 AM, inserted field deleted false, inserted field hidden false, inserted field position 400.

6 months ago User peltorator inserted blog post An interesting way to solve 739E by krismaz: inserted field blogEntryId 50036, inserted field catalogFolder Dynamic Programming, inserted field creationTime Sep 24, 2022, 9:42:08 PM, inserted field deleted false, inserted field englishDescription random-shuffle sqrt dp optimization, inserted field hidden false, inserted field position 1100, inserted field russianDescription random-shuffle корневая оптимизация динамики.

6 months ago User -is-this-fft- updated blog post Analysis of polynomial hashing by imachug: updated field position 5400.

6 months ago User -is-this-fft- updated blog post Anti-hash test. by Zlobober: updated field position 4500.

6 months ago User -is-this-fft- updated blog post Analysis of polynomial hashing by imachug: updated field position 6500.

6 months ago User -is-this-fft- updated blog post Kapun's algorithm by imachug: updated field position 5600.

6 months ago User -is-this-fft- updated blog post [Tutorial] Rolling hash and 8 interesting problems [Editorial] by dmkozyrev_thinks_slowly: updated field position 3200.

6 months ago User -is-this-fft- updated blog post On the mathematics behind rolling hashes and anti-hash tests by dacin21: updated field position 2300.

6 months ago User -is-this-fft- updated blog post [Tutorial] Rolling hash and 8 interesting problems [Editorial] by dmkozyrev_thinks_slowly: updated field position 4300.

6 months ago User -is-this-fft- updated blog post Anti-hash test. by Zlobober: updated field position 3400.

6 months ago User -is-this-fft- updated blog post [Tutorial] Rolling hash and 8 interesting problems [Editorial] by dmkozyrev_thinks_slowly: updated field position 5400.

6 months ago User -is-this-fft- updated blog post Kapun's algorithm by imachug: updated field position 4500.

Catalog

General Advice

How to come up with solutions?
- How to read problem statements – Um_nik – 4 years ago Collection of problems with solutions, with an emphasis on reading the problem statement
- How to come up with the solutions: techniques – MikeMirzayanov – 8 years ago
- Characteristics of the optimal solution, a technique for finding observations in a problem – Proofy – 14 months ago
- On "is this greedy or DP", forcing and rubber bands – -is-this-fft- – 7 months ago
- How to prove your solutions in Competitive Programming – Everule – 2 months ago
How to practice?
- F.A.Q. (in PM) – Um_nik – 6 years ago
- My opinion on how to practice competitive programming – Radewoosh – 22 months ago
- Self-deception: maybe why you're still grey after practicing every day – -is-this-fft- – 15 months ago
- How to practice Competitive Programming [Um_nik version] – Um_nik – 15 months ago
- [Tutorial] A way to Practice Competitive Programming : From Rating 1000 to 2400+ – E869120 – 4 years ago
How to ask for help?
- How to ask for help in PM – -is-this-fft- – 2 years ago
- Asking for help FAQ – Errichto – 4 years ago
How to use Codeforces [GUIDE] – SlavicG – 14 months ago
[Tutorial] The command line: how to read input from file without #ifdef and much more – -is-this-fft- – 11 months ago
After a Round FAQ – djm03178 – 10 months ago

Algorithms

General General discussions that cannot be attributed to a specific topic
- The Ultimate Topic List (with Resources, Problems and Templates) – YouKn0wWho – 18 months ago
- General ideas – adamant – 6 years ago
- A bit more of general ideas – adamant – 9 months ago
- [Tutorial] Collection of little techniques – -is-this-fft- – 12 months ago
Binary and Ternary Searches
- EDU: Binary Search – pashka – 3 years ago
- [Tutorial] Binary search and other "halving" methods – nor – 17 months ago
- Bin search and relative error – Um_nik – 6 years ago
- Multi-dimensional ternary search – adamant – 15 months ago
- Parallel Binary Search [tutorial] – himanshujaju – 7 years ago
- An alternative and very interesting approach on binary search – Pankin – 3 years ago
Constructive Algorithms
- Tips on Constructive Algorithms – ReaLNero – 3 years ago
Data Structures
- Fenwick Tree BIT
  
  [Tutorial] Searching Binary Indexed Tree in O(log(N)) using Binary Lifting – sdnr1 – 5 years ago
  
  [Tutorial] Path sum queries on a tree using a Fenwick tree – dolphingarlic – 3 years ago
  
  [Tutorial] A Bit of Math, Historic Sum, and Range Add Range Sum Binary Indexed Tree (Fenwick Tree) – FHVirus – 13 months ago
- Segment Tree
  
  EDU: Segment Tree, part 1 – pashka – 3 years ago
  
  Algorithm Gym :: Everything About Segment Trees – PrinceOfPersia – 8 years ago
  
  Efficient and easy segment trees – Al.Cash – 8 years ago
  
  crazySegmentTree: Segment Tree implementation with 5x faster queries than bottom-up tree – imachug – 2 years ago
  
  Compressed segment trees and merging sets in O(N logU) – bicsi – 2 years ago
  
  A simple introduction to "Segment tree beats" – jiry_2 – 5 years ago
  
  Video: Segment Tree Beats – peltorator – 23 months ago
  
  [Tutorial] Li Chao Tree Extended – rama_pang – 2 years ago
  
  using merging segment tree to solve problems about sorted list – TLE – 6 years ago
  
  [Tutorial] XOR Segment Tree – PurpleCrayon – 8 months ago
- Binary Search Trees Cartesian trees, AVL-trees, etc
  
  Algorithms Thread 9: Treaps (+ Gym Contest!) – SecondThread – 2 years ago
  
  Link-cut tree tutorial – ramchandra – 3 years ago
  
  Maintain subtree information using link/cut trees – ouuan – 4 years ago
  
  [Tutorial] Subtree lazy propagation on the link-cut tree – QCFium – 3 years ago
  
  Link Cut Tree implementation – bicsi – 3 years ago
  
  [Tutorial] Splay Tree: One Tree to Rule Them All – Zhtluo – 5 months ago
  
  "Merging treaps" -- or how to merge sorted sets in good complexity... – bicsi – 5 months ago
- Disjoint Set Union DSU
  
  EDU: DSU – Aksenov239 – 3 years ago
  
  [Tutorial] Proving the inverse Ackermann complexity of Union-Find – -is-this-fft- – 15 months ago
- Persistence
  
  AlgorithmsThread 5: Persistent Data Structures – SecondThread – 3 years ago
- Algorithm Gym :: Data structures – PrinceOfPersia – 8 years ago
- [Tutorial] Li Chao Tree Extended – rama_pang – 2 years ago
- [Tutorial] Supporting Queue-like Undoing on DS – Noam527 – 2 years ago
- Video about Disjoint Sparse Table or how to answer all queries in constant time – peltorator – 2 years ago
- On Multidimensional Range Queries – Laakeri – 3 years ago Proof (assuming ETH) of the nonexistence of certain data structures
- [Tutorial] A powerful representation of integer sets – brunomont – 2 years ago
- [Tutorial] Kinetic Tournament (Used in FBHC Round 2) – ekzhang – 3 years ago
- Tutorial on Permutation Tree (析合树） – errorgorn – 3 years ago
- Introduction to New Data Structure: Wavelet Trees – rachitiitr – 6 years ago
- [Tutorial] Sparse table – AlexLuchianov – 12 months ago
- Submask range queries – adamant – 10 months ago O(2^{n/2}) for masks of length n
- A slightly alternative approach for implementation of optimal LCA – monsoon – 4 years ago
- [Tutorial] Supporting Priority-Queue-like Undoing on DS – Monogon – 3 months ago
- [Tutorial] On Range LIS Queries, Part 1 – ko_osaga – 2 months ago
- [Tutorial] On Range LIS Queries, Part 2 – ko_osaga – 2 months ago
Divide-and-conquer
- Dynamic connectivity problem – adamant – 8 years ago
- Divide and conquer. Dynamic connectivity offline and DP optimization. Divide and conquer by queries. – Wind_Eagle – 9 months ago
Dynamic Programming DP
- [Tutorial] Non-trivial DP Tricks and Techniques – zscoder – 6 years ago
- Slope trick explained – Kuroni – 3 years ago
- An Introduction to Plug DP – 4fecta – 22 months ago DP on Broken Profile
- Dynamic Programming Optimizations – indy256 – 10 years ago
- SOS Dynamic Programming [Tutorial] – usaxena95 – 7 years ago
- Incredibly beautiful DP optimization from N^3 to N log^2 N – linkret – 6 years ago
- Theoretical grounds of lambda optimization – adamant – 15 months ago Aliens Trick
- [Tutorial] Knapsack, Subset Sum and the (max,+) Convolution – errorgorn – 15 months ago
- [Tutorial]Using Segment Trees to solve Dynamic Programming problems – AlexLuchianov – 12 months ago
- 1D1D-optimization (1D1D-optimization) – seiko.iwasawa – 20 months ago
- An interesting way to solve 739E – krismaz – 6 years ago random-shuffle sqrt dp optimization
- SMAWK algorithm as an alternative for D&C optimization – ko_osaga – 3 months ago
Geometry
- [Tutorial] Voronoi Diagram and Delaunay Triangulation in O(n log n) with Fortune's Algorithm – Monogon – 2 years ago
- O(n) algorithm for finding largest triangle in a convex is wrong? – u0qyz1234 – 6 years ago
- Efficient 3D Convex Hull Tutorial – Monogon – 3 years ago
- Dynamic convex hull implementation – dragonslayerintraining – 3 years ago
- Geometry: Polygon algorithms – Al.Cash – 6 years ago
- Half-plane intersection (Blogewoosh #5 (with images from now)) – Radewoosh – 5 years ago
- Quaternion algebra and geometry – adamant – 7 years ago
- Easy geometry using std::complex – Hikari9 – 7 years ago
- Geometry: 2D points and lines [Tutorial] – Al.Cash – 6 years ago
- [Tutorial] Solving Interval Problems with Geometry – Monogon – 15 months ago
- AlgorithmsThread Episode 6: Convex Hull Tricks – SecondThread – 3 years ago
- Visualization tool for 2D problems (C++) – kalinov – 3 years ago
- Some rotational invariants in geometry – adamant – 14 months ago
- Easy online point location algorithm – qwerty787788 – 6 months ago
Games
- A blog on the Sprague-Grundy Theorem – sirknightingfail – 4 years ago
- The Intuition Behind NIM and Grundy Numbers in Combinatorial Game Theory – Shisuko – 4 years ago
- [Tutorial] Slight Generalization of Grundy Numbers – emorgan5289 – 2 years ago Transfinite Grundy numbers
- Nimbers and Sprague-Grundy theorem – adamant – 10 months 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- – 4 years ago
  
  My own algorithm — offline incremental strongly connected components in O(m*log(m)) – Radewoosh – 22 months ago
- Shortest Paths
  
  0-1 BFS [Tutorial] – himanshujaju – 7 years ago
  
  [Tutorial] k shortest paths and Eppstein's algorithm – meooow – 11 months ago
  
  Rethink the Dijkstra algorithm -- Let's go deeper – CristianoPenaldo – 6 months ago
- Trees
  
  Algorithms Thread 8: Tree Basics (+ Gym Contest) – SecondThread – 3 years ago Finding diameters, binary lifting and flattening
  
  A list of important concepts in Tree-based Problems – dvdg6566 – 2 years ago
  
  Hybrid Tutorial #-1: Heavy-Light Decomposition – galen_colin – 3 years ago
  
  Heavy-light decompositon — it can be simple! – Vladyslav – 9 years ago
  
  Easiest HLD with subtree queries – adamant – 6 years ago
  
  [Tutorial] Sack (dsu on tree) – Arpa – 7 years ago Small-to-large merging
  
  Hybrid Tutorial #-2: Centroid Decomposition – galen_colin – 3 years ago
  
  Heavy-light decomposition implementation – Al.Cash – 7 years ago
  
  [Tutorial] Path sum queries on a tree using a Fenwick tree – dolphingarlic – 3 years ago
  
  Bridge Trees [Tutorial] – aryan12 – 14 months ago
  
  Line tree (Path max queries on a tree in O(1)) – neal – 3 years ago Description is in Kaban-5 comment
  
  [Tutorial] Binary lifting – AlexLuchianov – 13 months ago
  
  [Tutorial] Tree Isomorphism CSES – Olympia – 12 months ago
  
  [Tutorial] Diameter of a tree and its applications – TheScrasse – 12 months ago
  
  [Tutorial] Fully Dynamic Trees Supporting Path/Subtree Aggregates and Lazy Path/Subtree Updates – smax – 10 months ago
  
  [Tutorial] Theoretically Faster HLD and Centroid Decomposition – errorgorn – 8 months ago
  
  [Insight] Number of Topological Orderings of a Directed Tree – Osama_Alkhodairy – 3 years ago
- Matchings
  
  [Tutorial] Blossom Algorithm for General Matching in O(n^3) – Monogon – 21 month(s) ago
  
  Randomized general matching with Tutte matrix – adamant – 21 month(s) ago
- Flows
  
  [Tutorial, Flows] Project Selection Problem – AlexLuchianov – 12 months ago
  
  [Tutorial] My way of understanding Dinitz's ("Dinic's") algorithm – -is-this-fft- – 8 months ago
  
  [Tutorial] Minimum cost (maximum) flow – -is-this-fft- – 8 months ago
  
  [Tutorial] More about minimum cost flows: potentials and Dinitz – -is-this-fft- – 8 months ago
  
  [Tutorial] Network simplex – brunovsky – 19 months ago
  
  Kőnig's and Hall's theorems through minimum cut in bipartite graphs – adamant – 8 months ago
- Heuristic algorithm for Hamiltonian path in directed graphs – fantasy – 23 months ago
- [Tutorial] Graph Potentials, Johnson's Algorithm, and Min Cost Max Flow – Monogon – 18 months ago
- Algorithm Gym :: Graph Algorithms – PrinceOfPersia – 8 years ago
- [Tutorial] Boruvka's Algorithm – RockyB – 3 years ago
- Traversing the complement graph in linear/near-linear time in multiple ways – nor – 20 months ago
- Story about edge coloring of graph – ko_osaga – 3 years ago Vizing's Theorem
- Merging Queries Trick – SlavicG – 13 months ago
Greedy Algorithms
- [Tutorial] Matroid intersection in simple words – ATSTNG – 4 years ago
- [Tutorial] Greedoids: a formal way to look at families of greedily-solvable problems – nor – 3 months ago
Hashing
- Blowing up unordered_map, and how to stop getting hacked on it – neal – 4 years ago
- [Tutorial] Rolling hash and 8 interesting problems [Editorial] – dmkozyrev_thinks_slowly – 5 years ago
- On the mathematics behind rolling hashes and anti-hash tests – dacin21 – 5 years ago
- Analysis of polynomial hashing – imachug – 13 months ago
- Anti-hash test. – Zlobober – 11 years ago
- Kapun's algorithm – imachug – 13 months ago
Mathematics
- Bitwise Operations
  
  Bitwise operations for beginners – Errichto – 3 years ago
  
  Bitwise operations 2 — popcount & bitsets – Errichto – 3 years ago
  
  A Beautiful Technique for Some XOR Related Problems – DrSwad – 4 years ago Gaussian elimination, a.k.a xor basis
  
  XOR basis without linear algebra – Everule – 13 months ago
- Number Theory
  
  [Tutorial] Generalized Möbius Inversion on Posets – nor – 15 months ago
  
  [Tutorial] Catalan Numbers and Catalan Convolution – Dardy – 2 years ago
  
  Short modular inverse – _h_ – 7 years ago
  
  Counting Divisors of a Number in $O(N^{\frac{1}{3}})$ [tutorial] – himanshujaju – 7 years ago
  
  Counting primes in $\tilde{{\cal O}}(n^{2/3}\,\,)$ – Maksim1744 – 22 months ago
  
  Finding minimum residue of a linear function in O(log M) time – mango_lassi – 23 months ago
  
  On the Min25 sieve and extensions / SPOJ ASSIEVE – box – 21 month(s) ago
  
  [Tutorial] Math note — Möbius inversion – Nisiyama_Suzune – 6 years ago
  
  [Tutorial] Math note — Dirichlet convolution – Nisiyama_Suzune – 6 years ago
  
  Essential Elementary Number Theory (Essentials of Elementary Number Theory) – Everule – 16 months 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 – 15 months ago
  
  On continued fractions. Part 3: In competitive programming – adamant – 12 months ago
  
  p-adic exponent or why there is a primitive root modulo powers of prime numbers (except 2) – adamant – 10 months ago
  
  [Tutorial] Berlakamp's Algorithm for Polynomial Factorization in a Field (1698G buffed) – errorgorn – 9 months ago
  
  [Tutorial] Euler's phi function, its properties, and how to compute it – kamilszymczak1 – 7 months ago
  
  Implicit Prime Factorisation – Everule – 5 months ago
- Probability Theory
  
  Sums and Expected Value — part 1 – Errichto – 4 years ago
  
  Sums and Expected Value — part 2 – Errichto – 4 years ago
  
  [Tutorial] Expected number of coin flips required to achieve a given string – gabrielwu – 15 months ago
  
  Intuition and application of Martingales (Probability 101, the intuition behind martingales and solving problems with them) – nor – 3 months ago Applying results of Martingales to prove a wide variety of claims.
- Сombinatorics
  
  [Tutorial] Inclusion-Exclusion Principle – Roundgod – 4 years ago
  
  Young Tableaus and the Hook Length Formula – mango_lassi – 15 months ago
  
  [Tutorial] Burnside's lemma (with example) – TwoFx – 4 years ago
  
  [Tutorial] Invariants and Monovariants – TooNewbie – 5 years ago
  
  Catalan Numbers and Generating Uniform Balanced Bracket Sequences – errorgorn – 10 months ago
  
  An intuition and simpler proof for Kirchoff's tree theorem – Everule – 10 months ago
  
  Lattice paths and Lindström–Gessel–Viennot lemma – miaowtin – 5 months ago
- Linear Algebra
  
  A Beautiful Technique for Some XOR Related Problems – DrSwad – 4 years ago Gaussian elimination
  
  Linear Basis (Xor Basis Extended) – errorgorn – 15 months ago Generalization of Gaussian elimination to integers modulo a composite number (and beyond).
  
  2 Special cases of Gaussian [Tutorial] – MazzForces – 5 years ago Markov Chains (for Cyclic Expected Values) and the "XOR basis" technique
- Permutations
  
  [Tutorial] A comprehensive guide to permutations for beginners – nor – 3 months ago
  
  Tutorial on Permutation Tree (析合树） – errorgorn – 3 years ago
  
  Permutation group basis construction (Schreier–Sims algorithm) – adamant – 3 months ago
- Polynomials, Series and Recurrences
  
  Generating Functions General theory; algorithms are under FFT
  
  [Tutorial] Generating Functions in Competitive Programming (Part 1) – zscoder – 3 years ago
  
  [Tutorial] Generating Functions in Competitive Programming (Part 2) – zscoder – 3 years ago
  
  A problem collection of ODE and differential technique – amiya – 3 years ago
  
  Prefix Sum Polynomial – Lain – 15 months ago
  
  Combinatorial species: An intuition behind generating functions – adamant – 9 months ago Simple way to construct generating functions and interpret operations on them.
  
  Unlabeling combinatorial species (cycle index series) – adamant – 2 months ago Finding OGFs for unlabeled species composition
  
  Moment-generating functions, inversions and q-analogs – adamant – 14 months ago
  
  OGFs, EGFs, differentiation and Taylor shifts – adamant – 14 months ago
  
  Fast polynomial composition – adamant – 11 months ago Given A(x) and B(x), compute first n coefficients of A(B(x)).
  
  Lagrange inversion theorem – adamant – 9 months ago Given x = f(y), find coefficients of g(x) such that y = g(x).
  
  Partitions and pentagonal number theorem – adamant – 9 months ago Explicit formula for (1-x)(1-x^2)(1-x^3)... and applications
  
  FFT and Similar Transformations Algorithms for operating on polynomials
  
  [Tutorial] FFT – -is-this-fft- – 2 months ago
  
  Tutorial on FFT/NTT — The tough made simple. ( Part 1 ) – sidhant – 7 years ago
  
  Notes on FFT / NTT, and the "ultimate" NTT with modulus > 9 * 10^18 – Spheniscine – 3 years ago
  
  On Fast Fourier Transform – adamant – 5 years ago
  
  Operations on Formal Power Series – rng_58 – 5 years ago
  
  Operations on polynomials (on cp-algorithms) – adamant – 4 years ago Fast polynomial division, evaluation, interpolation.
  
  [Tutorial] Generalized Chirp Z-Transform – box – 2 years ago
  
  Discrete Fourier Transform eigenvalues – adamant – 22 months ago
  
  A simple way to understand the transposed algo of multi-eval (A simple way to understand the transposed algo of multi-eval) – hly1204 – 13 months ago
  
  An unexpected D&C with FFT – Um_nik – 10 months ago
  
  Introducing the imaginary cyclic convolution, speeding up convolution by a factor of 2 – pajenegod – 6 months ago
  
  Fast convolution for 64-bit integers – quasisphere – 7 years ago
  
  CDQ convolution (online FFT) generalization with Newton method – adamant – 2 months ago
  
  Bitwise Convolutions Xor-, or- and subset convolution, "set power series"
  
  Generalized FWHT: How I realized I did not understand FWHT – errorgorn – 17 months ago
  
  Tutorial on Zeta Transform, Mobius Transform and Subset Sum Convolution – sidhant – 3 years ago
  
  Fast Walsh Hadamard Transforms and it's inner workings – upobir – 3 years ago
  
  Subset convolution interpretation – adamant – 21 month(s) ago
  
  Optimal Algorithm on Polynomial Composite Set Power Series – Elegia – 21 month(s) ago
  
  Linear Recurrences
  
  Matrix Exponentiation tutorial + training contest – Errichto – 3 years ago
  
  On linear recurrences and the math behind them – adamant – 13 months ago
  
  Recovering a linear recurrence with the extended Euclidean algorithm – adamant – 12 months ago
  
  Half-GCD algorithm – adamant – 12 months ago Compute polynomial GCD or recover minimum recurrence in O(n log^2 n)
  
  Linear Recurrence and Berlekamp-Massey Algorithm – TLE – 5 years ago
  
  [Tutorial] Berlekamp-Massey – smax – 17 months ago
  
  [Math note] On the relationship between gf and me – -is-this-fft- – 21 month(s) 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 – 16 months 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 – 10 months ago
  
  Lagrange interpolation and partial fraction decomposition – adamant – 15 months ago
- Optimization Anything related to mathematical optimization
  
  Multi-dimensional ternary search – adamant – 15 months ago
  
  Theoretical grounds of lambda optimization – adamant – 15 months ago Aliens Trick
  
  Duality in linear programming. Part 1 — definition and construction – adamant – 8 months ago
  
  Duality in linear programming. Part 2 — in competitive programming – adamant – 8 months ago
- Abstract nonsense Abstract algebra and friends
  
  Permutation group basis construction (Schreier–Sims algorithm) – adamant – 3 months ago
  
  Associativity and general identity testing – adamant – 22 months ago
- [Tutorial] 2-SAT – arujbansal – 20 months ago
- 2-SAT Tutorial – HosseinYousefi – 8 years ago
- An interesting algebraic construction – box – 21 month(s) ago
Non-exact and Randomized Algorithms
- [Tutorial] Simulated Annealing in Competitive Programming – PurpleCrayon – 19 months ago
- Randomized algorithms lecture, part 1 & 2 – Errichto – 3 years ago
- Blogewoosh #1 – Radewoosh – 5 years ago
- Blogewoosh #6 – Radewoosh – 4 years ago
- On the Number of Runs at the Monte-Carlo Method – rotavirus – 2 years ago
- Randomized general matching with Tutte matrix – adamant – 21 month(s) ago
- How randomized solutions can be hacked, and how to make your solution unhackable – neal – 5 years ago
Sortings
- Lecture #3 — Exchange arguments (sorting with dp) – Errichto – 4 years ago
Square Root Techniques SQRT decomposition, Mo's algorithm, etc
- [Tutorial] Square Root Techniques – Errichto – 17 months ago
- An alternative sorting order for Mo's algorithm – gepardo – 5 years ago
- Mo's Algorithm on Trees [Tutorial] – animeshf – 7 years ago
- Sqrt-tree: answering queries in O(1) with O(NloglogN) preprocessing. – gepardo – 5 years ago
- [Tutorial] Square root decomposition and applications – box – 2 years ago
- Unknown Data Structure — (Sqrt Fragmented Tree) – cjtoribio – 7 years ago
- [Tutorial] Subset Sum Square Root Optimisation – arujbansal – 16 months ago
Strings
- [Tutorial] Dynamic Suffix Arrays – brunomont – 20 months ago
- On suffix automaton (and tree) – adamant – 7 years ago
- Aho-Corasick algorithm. Construction – adamant – 8 years ago
- A short guide to suffix automata – quasisphere – 7 years ago
- Palindromic tree: behind the scenes – adamant – 9 years ago
- A bit more about palindromes – adamant – 8 years ago You're given a string, split it into the minimum number of palindromes.
- The history of some recurring problem – adamant – 4 years ago You're given a string s and queries: how many distinct substrings does sl...sr have?
- Suffix tree. Ukkonen's algorithm – adamant – 8 years ago
- [Tutorial] Expected number of coin flips required to achieve a given string – gabrielwu – 15 months ago
- [Tutorial] Dictionary of Basic Factors — O(1) String Matching – Leonardo16 – 21 month(s) ago
- Z Algorithm – paladin8 – 11 years ago
- [Tutorial] On Variations of String Matching – brunomont – 2 months ago
- Random notes on Lyndon decomposition – ko_osaga – 7 months ago
Sweeping Line
- How to sweep like a Sir – DanAlex – 8 years ago
- [Tutorial] Finding inclusion hierarchy among circles — An implementation of a sweep-line algorithm – Arpa – 15 months ago
Two Pointers
- EDU: Two Pointers Method – pashka – 2 years ago

Programming Languages

C++
- C++ Tricks – HosseinYousefi – 8 years ago
- Catching silly mistakes with GCC – andreyv – 8 years ago
- Don't use rand(): a guide to random number generators in C++ – neal – 5 years ago
- [Tutorial] GCC Optimization Pragmas – nor – 17 months ago
- C++ tips and tricks – Golovanov399 – 3 years ago
- Performance tip : using std::deque as a memory cache – mouse_wireless – 5 years ago
- C++ STL: Policy based data structures – adamant – 9 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 – 9 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 – 12 years ago
- Tutorial on SIMD vectorisation to speed up brute force – maomao90 – 15 months ago
- Generic data structure templates via C++ mixins – clam – 22 months ago
- Explanation to weird/strange floating point behaviour in C++ – pajenegod – 3 years ago Why you sometimes get WA with 64-bit but not 32-bit compiler
- How NOT to use macros – AlexLuchianov – 12 months ago
- How to get actual 64 bit bitsets on Codeforces [Not Recommended] [Don't do this at your job] – Chilli – 3 years ago
- [Tutorial] Writing C++ like Python: tricks Python doesn't want you to know – nor – 3 months ago
D
- The D programming language in competitive programming – Gassa – 5 years ago

Meta Posts that are important for competitive programming as a whole

Tools
- CF-Predictor — Know your rating changes! – WasylF – 6 years ago
- Multiple rating graph with other accounts – yak_ex – 12 years ago
- Have you already seen the history of ratings on clist? – aropan – 3 years ago Rating aggregation from different competitive programming sites.
- Codeforces Extensions – MohamedAboOkail – 3 years ago
- Gym Finder – NightRage – 15 months ago
- Userscript: table view in Catalog – -is-this-fft- – 12 months ago
Libraries
- AtCoder Library – rng_58 – 3 years ago A professionally-developed competitive programming library.
- New online judge: Library-Checker! – yosupo – 3 years ago
- (The Ultimate) Code Library – YouKn0wWho – 18 months ago
Announcements Resources that help keeping track of upcoming contests.
- pe in 30 – Golovanov399 – 15 months ago Telegram channel with 30-minutes announcements for new problems at projecteuler.
- Resource clist.x10.mx moved to clist.by – aropan – 11 years ago Contest calendar and more

Problem and Contest Preparation

Testing and Polygon
- Briefly about testlib.h – MikeMirzayanov – 8 years ago
- Generators with testlib.h – MikeMirzayanov – 8 years ago
- Validators with testlib.h – I_love_Hoang_Yen – 8 years ago
- Checkers with testlib.h – Zlobober – 8 years ago
- Interactors with testlib.h – PrinceOfPersia – 8 years ago
- 10 Reasons to Prepare Problems in Polygon – MikeMirzayanov – 8 years ago
- [Tutorial] Polygon.Codeforces Tutorial - A Guide to Problem Preparation [Part 1] – darkkcyan – 12 months ago
- Polygon Updates (Fall-Winter 2014) – Avalanche – 8 years ago
- Testlib and Polygon Updates (June, 2015) – fcspartakm – 8 years ago
- Testlib and Polygon Updates [July, 2018] – MikeMirzayanov – 5 years ago
- Polygon updates (June-October 2019) – geranazavr555 – 3 years ago
- Polygon Updates (June — August 2021) – unreal.eugene – 19 months ago
- Testlib: Opts — parsing command line options – MikeMirzayanov – 3 years ago
- Testlib: tests + CI – MikeMirzayanov – 8 months ago
Problemsetting Interviews with problemsetters, how to come up with problem ideas etc.
- How to come up with problem ideas – Lewin – 4 years ago
- On problemsetting – antontrygubO_o – 3 years ago
- On problemsetting 2 – antontrygubO_o – 3 years ago
- Way of problemsetter – Sammarize – 9 years ago
- What is it like to be a problem writer? – Nickolas – 11 years ago
- Problemsetter's Memoir – Nickolas – 9 years ago
- About Problemsetting (for AtCoder and Codeforces) – dario2994 – 2 years ago

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