Repo Problem Index¶

This page lists every current solved problem note in the repo and maps it back to the learning structure.

Total tracked problem notes: 158
Data files: problem-catalog.json, repo-problem-catalog.csv
Fastest route: Problem Finder when you want filters instead of the full static table
External companion index: external-problem-index.md
Topic maps: topic-maps/index.md
Recommended use: start from the Primary topic, open the Topic map, then solve from the linked notes.

Coverage Snapshot¶

Area	Count
Foundations	11
Data Structures	26
Graphs	33
DP	19
Greedy	4
Math	26
Combinatorics	5
Strings	12
Geometry	11
Advanced	11

Current Catalog¶

Foundations¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`FACTORYMACHINES`	Factory Machines	`Foundations -> Binary Search`	Foundations -> Complexity And Invariants	answer binary search; monotone feasibility; production rate accumulation	`medium`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`INCREASINGARRAY`	Increasing Array	`Foundations -> Complexity And Invariants`	-	loop invariant scan; greedy repair; running maximum maintenance	`easy`	CSES, Introductory problems	Map / Ladder / Tutorial	Note	Code
`MISSINGNUMBER`	Missing Number	`Foundations -> C++ Language`	-	running total subtraction; arithmetic series sum; type safe warm-up	`easy`	CSES, Introductory problems	Map / Ladder / Tutorial	Note	Code
`WEIRDALGORITHM`	Weird Algorithm	`Foundations -> C++ Language`	-	simulation loop; parity branching; first local workflow	`easy`	CSES, Introductory problems	Map / Ladder / Tutorial	Note	Code
`RANGEUPDATEQUERIES`	Range Update Queries	`Foundations -> Difference Arrays`	Data Structures -> Fenwick Tree	difference array updates; fenwick on diff; range add point query	`medium`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`STATICRANGESUMQUERIES`	Static Range Sum Queries	`Foundations -> Prefix Sums`	-	prefix sum build; range sum by subtraction; immutable array queries	`easy`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`FERRISWHEEL`	Ferris Wheel	`Foundations -> Sorting`	Foundations -> Two Pointers	opposite end pointers; greedy pairing; sorted capacity matching	`easy-medium`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`MOVIEFESTIVAL`	Movie Festival	`Foundations -> Sorting`	Foundations -> Complexity And Invariants	finish-time sorting; interval scheduling; exchange argument greedy	`easy`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`DISTINCTNUMBERS`	Distinct Numbers	`Foundations -> STL Basics`	Foundations -> C++ Language	sort unique; container deduplication; stl algorithms	`easy`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`APARTMENTS`	Apartments	`Foundations -> Two Pointers`	Foundations -> Sorting	two sorted pointers; tolerance matching; greedy monotone scan	`easy-medium`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`SUMOFTWOVALUES`	Sum of Two Values	`Foundations -> Two Pointers`	Foundations -> Sorting	sort and scan; opposite end pointers; index restoration	`medium`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code

Data Structures¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`BTREEDICTIONARY`	B-Tree Dictionary	`Data Structures -> B-Trees`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`VASILIYSMULTISET`	Vasiliy's Multiset	`Data Structures -> Binary Trie / XOR Queries`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`C11XU`	Bộ sưu tập đồng xu	`Data Structures -> DSU`	Advanced -> Optimization And Duality	xor-independence; forest selection; augmenting exchange	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`DISTINCTCOLORS`	Distinct Colors	`Data Structures -> DSU On Tree / Small-To-Large`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`DYNAMICCONNECTIVITY`	Dynamic Connectivity	`Data Structures -> DSU Rollback / Offline Dynamic Connectivity`	Data Structures -> DSU; Data Structures -> Offline Tricks	dsu rollback; segment tree over time; offline dynamic connectivity	`hard`	CSES, Advanced techniques	Map / Ladder / Tutorial	Note	Code
`CVP00001`	Ô ăn quan	`Data Structures -> Fenwick Tree`	Foundations -> Prefix Sums	circular updates; range-add point-query; query-from-initial-state	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`CONCERTTICKETS`	Concert Tickets	`Data Structures -> Heaps And Ordered Sets`	-	multiset predecessor; erase one occurrence; greedy ticket assignment	`medium`	CSES, Sorting and searching	Map / Ladder / Tutorial	Note	Code
`RESERVATIONSYSTEM`	Reservation System	`Data Structures -> Interval Trees`	-	-	`easy`	-	Map / Ladder / Tutorial	Note	Code
`HORRIBLEQUERIES`	Horrible Queries	`Data Structures -> Lazy Segment Tree`	-	lazy segment tree; range add range sum; deferred propagation	`medium`	SPOJ, Range queries	Map / Ladder / Tutorial	Note	Code
`NEARESTSMALLERVALUES`	Nearest Smaller Values	`Data Structures -> Monotonic Stack / Queue`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`POWERFULARRAY`	Powerful Array	`Data Structures -> Mo's Algorithm`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`WILLEMCHTHOLLYANDSENIORIOUS`	Willem, Chtholly and Seniorious	`Data Structures -> ODT / Chtholly`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`DISTINCTVALUESQUERIES`	Distinct Values Queries	`Data Structures -> Offline Tricks`	Data Structures -> Fenwick Tree	offline right-endpoint sweep; last occurrence activation; fenwick range count	`hard`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`MERGEABLEHEAP1`	P3377 [Template] Mergeable Heap 1	`Data Structures -> Pairing Heap / Leftist Heap`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`ORDERSET`	Order Statistic Set	`Data Structures -> PBDS / Order Statistics Tree`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`RANGEQUERIESANDCOPIES`	Range Queries and Copies	`Data Structures -> Persistent Data Structures`	Data Structures -> Segment Tree	persistent segment tree; path copying; versioned range sum	`hard`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`PERSISTENTLIST`	Persistent List	`Data Structures -> Persistent Treap`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`DYNAMICRANGESUMQUERIES`	Dynamic Range Sum Queries	`Data Structures -> Segment Tree`	-	iterative segment tree; point assignment; range sum query	`medium`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`RANGECHMINCHMAXADDRANGESUM`	Range Chmin Chmax Add Range Sum	`Data Structures -> Segment Tree Beats`	-	segment tree beats; range chmin; range chmax; second extremum summaries	`hard`	Library Checker, Verification	Map / Ladder / Tutorial	Note	Code
`SKIPLISTDICTIONARY`	Skiplist Dictionary	`Data Structures -> Skip Lists`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`STATICRANGEMINIMUMQUERIES`	Static Range Minimum Queries	`Data Structures -> Sparse Table`	-	sparse table rmq; idempotent overlap query; log table preprocessing	`easy`	CSES, Range queries	Map / Ladder / Tutorial	Note	Code
`ORDINARYBALANCEDTREE`	普通平衡树	`Data Structures -> Splay Tree`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`CUTANDPASTE`	Cut and Paste	`Data Structures -> Treap / Implicit Treap`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`SALARYQUERIES`	Salary Queries	`Data Structures -> Treap / Implicit Treap`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`MKTHNUM`	K-th Number	`Data Structures -> Wavelet Tree`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`XFASTDICTIONARY`	X-Fast Dictionary	`Data Structures -> X-Fast / Y-Fast Tries`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code

Graphs¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`MESSAGEROUTE`	Message Route	`Graphs -> BFS And DFS`	Graphs -> Graph Modeling	breadth-first search; unweighted shortest path; parent reconstruction	`easy`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`NECESSARYROADS`	Necessary Roads	`Graphs -> Bridges, Articulation, And BCC`	-	low-link; bridge detection; dfs tree critical edge	`medium`	CSES, Advanced techniques	Map / Ladder / Tutorial	Note	Code
`CIELTHECOMMANDER`	Ciel the Commander	`Graphs -> Centroid Decomposition`	Graphs -> Trees	centroid decomposition; centroid tree labeling; balanced recursive split	`hard`	Codeforces, Tree decomposition	Map / Ladder / Tutorial	Note	Code
`DEBRUIJNSEQUENCE`	De Bruijn Sequence	`Graphs -> De Bruijn Sequence`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`SUBTREEQUERIES`	Subtree Queries	`Graphs -> Euler Tour / Subtree Queries`	Graphs -> Trees; Data Structures -> Fenwick Tree	euler tour flattening; subtree interval; fenwick point set range sum	`medium`	CSES, Tree algorithms	Map / Ladder / Tutorial	Note	Code
`DYNAMICTREEVERTEXADDSUBTREESUM`	Dynamic Tree Vertex Add Subtree Sum	`Graphs -> Euler Tour Tree`	-	-	`very hard`	-	Map / Ladder / Tutorial	Note	Code
`MAILDELIVERY`	Mail Delivery	`Graphs -> Eulerian Path / Cycle`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`FFLOW`	Fast Maximum Flow	`Graphs -> Maximum Flow`	Advanced -> Algorithm Engineering	maximum flow; undirected capacities; capacity scaling	`medium`	VN SPOJ, ICPC-style	Map / Ladder / Tutorial	Note	Code
`MAXIMUMFLOWPUSHRELABEL`	Maximum Flow	`Graphs -> Maximum Flow`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`MINCOST`	Luồng với chi phí nhỏ nhất	`Graphs -> Maximum Flow`	Graphs -> Min-Cost Flow	transportation network; flow reconstruction; duplicate-edge overwrite	`hard`	VN SPOJ, ICPC-style	Map / Ladder / Tutorial	Note	Code
`POLICECHASE`	Police Chase	`Graphs -> Maximum Flow`	Advanced -> Optimization And Duality	unit capacity max flow; residual reachable cut; minimum edge cut certificate	`medium`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`REACTORCOOLING`	Reactor Cooling	`Graphs -> Maximum Flow`	Graphs -> Flow With Lower Bounds	feasible circulation; lower bounds; flow reconstruction	`hard`	Codeforces acmsguru, Advanced techniques	Map / Ladder / Tutorial	Note	Code
`GENERALMATCHING`	Matching on General Graph	`Graphs -> Edmonds Blossom / General Matching`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`GLOBALMINCUT`	Minimum Cut	`Graphs -> Randomized / Global Min-Cut`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`MCQUERY`	MinCut Query	`Graphs -> Gomory-Hu Tree`	Data Structures -> DSU; Graphs -> Trees	all-pairs min-cut; cut tree; count pairs by threshold	`hard`	VN SPOJ, ICPC-style	Map / Ladder / Tutorial	Note	Code
`BUILDINGROADS`	Building Roads	`Graphs -> Graph Modeling`	-	connected components; component representatives; constructive graph connection	`easy`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`COUNTINGROOMS`	Counting Rooms	`Graphs -> Graph Modeling`	Graphs -> BFS And DFS	grid graph modeling; iterative flood fill; connected components	`easy`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`PATHQUERIES2`	Path Queries II	`Graphs -> Heavy-Light Decomposition`	Graphs -> Trees; Data Structures -> Segment Tree	heavy light decomposition; path query decomposition; segment tree on base array	`medium`	CSES, Tree algorithms	Map / Ladder / Tutorial	Note	Code
`TASKASSIGNMENT`	Task Assignment	`Graphs -> Hungarian / Assignment Problem`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`COMPANYQUERIES2`	Company Queries II	`Graphs -> LCA`	Graphs -> Trees	binary lifting; depth equalization; lowest common ancestor	`medium`	CSES, Tree algorithms	Map / Ladder / Tutorial	Note	Code
`DYNAMICTREEVERTEXADDPATHSUM`	Dynamic Tree Vertex Add Path Sum	`Graphs -> Link-Cut Tree`	-	-	`very hard`	-	Map / Ladder / Tutorial	Note	Code
`QBFLOWER`	Tặng hoa	`Graphs -> Matching`	-	minimum edge cover; general matching; graph transformation	`medium`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`SCHOOLDANCE`	School Dance	`Graphs -> Matching`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`ROADREPARATION`	Road Reparation	`Graphs -> Minimum Spanning Tree`	-	kruskal mst; connectivity check; cut property greedy	`medium`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`COURSESCHEDULE`	Course Schedule	`Graphs -> Topological Sort And SCC`	-	kahn topological sort; indegree peeling; cycle by failed ordering	`medium`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`QOS`	Chất lượng dịch vụ	`Graphs -> Shortest Paths`	DP -> Foundations	shortest path plus dp; kth lexicographic path; bounded slack states	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`STABLEMARRIAGE`	Stable Marriage	`Graphs -> Stable Marriage`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`VOSTRIP`	VOSTRIP	`Graphs -> Tree DP`	DP -> Tree DP; Graphs -> Trees	tree endpoint pairing; path decomposition; local imbalance formula	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`TREEISOMORPHISM1`	Tree Isomorphism I	`Graphs -> Tree Isomorphism`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`MTREECOL`	Color a tree	`Graphs -> Trees`	-	ratio greedy; tree contraction; exchange argument	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`VMWTREE`	Lại là cây khung	`Graphs -> Trees`	Data Structures -> Segment Tree; Graphs -> Heavy-Light Decomposition	path reverse; path sequence queries; heavy-light decomposition	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`GIANTPIZZA`	Giant Pizza	`Graphs -> Two-SAT`	Graphs -> Graph Modeling; Graphs -> Topological Sort And SCC	2-sat; implication graph; assignment extraction	`medium`	CSES, Graph algorithms	Map / Ladder / Tutorial	Note	Code
`KINGDOMANDITSCITIES`	Kingdom and its Cities	`Graphs -> Virtual Tree / Auxiliary Tree`	-	-	`very hard`	-	Map / Ladder / Tutorial	Note	Code

DP¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`SCHOOLEXCURSION`	School Excursion	`DP -> Bit-Parallelism / Bitset Optimization`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`VMMARBLE`	Phân loại bi	`DP -> Bitmask DP`	Advanced -> Constructive	final-color assignment; residual-state dp; capacity-2 moves	`medium`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`COUNTINGTILINGS`	Counting Tilings	`DP -> Broken Profile / Plug DP`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`LINEADDGETMIN`	Line Add Get Min	`DP -> Convex Hull Trick / Li Chao Tree`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`MONSTERGAME2`	Monster Game II	`DP -> Convex Hull Trick / Li Chao Tree`	-	li chao tree; affine dp; online line minimum	`hard`	CSES, Dynamic programming	Map / Ladder / Tutorial	Note	Code
`COUNTINGNUMBERS`	Counting Numbers	`DP -> Digit DP`	-	digit dp; previous digit state; range counting	`medium`	CSES, Dynamic programming	Map / Ladder / Tutorial	Note	Code
`CIELANDGONDOLAS`	Ciel and Gondolas	`DP -> Divide and Conquer DP`	-	-	`very hard`	-	Map / Ladder / Tutorial	Note	Code
`VMSCALE`	Chiếc cân kỳ diệu	`DP -> Foundations`	Math -> Number Theory Basics	budget dp; balanced ternary; decision-tree optimization	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`BITWISEXORCONVOLUTION`	Bitwise XOR Convolution	`DP -> FWHT / XOR Convolution / Subset Convolution`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`REMOVALGAME`	Removal Game	`DP -> Interval DP`	-	score difference dp; take from ends; interval minimax	`medium`	CSES, Dynamic programming	Map / Ladder / Tutorial	Note	Code
`BOOKSHOP`	Book Shop	`DP -> Knapsack Family`	Advanced -> Complexity And Hardness	0 1 knapsack; downward capacity loop; budget value maximization	`easy`	CSES, Dynamic programming	Map / Ladder / Tutorial	Note	Code
`KNUTHDIVISION`	Knuth Division	`DP -> Knuth Optimization`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`REDANDBLUELAMPS`	Red and Blue Lamps	`DP -> Lagrangian Relaxation / Aliens Trick`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`SLIDINGWINDOWMINIMUM`	Sliding Window Minimum	`DP -> Sliding Window And Window DP`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`TFIELD`	Ruộng bậc thang	`DP -> Sliding Window And Window DP`	Foundations -> Two Pointers; Geometry -> Polygon Area And Point Location	nested polygons; weighted sliding window; shoelace preprocessing	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`SNUKETOON`	Snuketoon	`DP -> Slope Trick`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`COMPATIBLENUMBERS`	Compatible Numbers	`DP -> SOS DP`	-	-	`2200`	-	Map / Ladder / Tutorial	Note	Code
`TREEDISTANCES2`	Tree Distances II	`DP -> Tree DP`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`TREEMATCHING`	Tree Matching	`DP -> Tree DP`	Graphs -> Trees	tree matching dp; matched or unmatched state; child swap contribution	`medium`	CSES, Tree algorithms	Map / Ladder / Tutorial	Note	Code

Greedy¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`HUFFMANCODING`	Huffman Coding Benchmark	`Greedy -> Huffman / Data Compression`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`LEMONADELINE`	Lemonade Line	`Greedy -> Prefix Constraints`	Foundations -> Sorting	descending tolerance order; prefix feasibility count; minimize accepted arrivals	`easy`	USACO, Greedy	Map / Ladder / Tutorial	Note	Code
`PREFIXSUMADDICTS`	Prefix Sum Addicts	`Greedy -> Prefix Constraints`	Foundations -> Prefix Sums	suffix prefix differences; sorted sequence feasibility; first block capacity bound	`medium`	Codeforces, Greedy	Map / Ladder / Tutorial	Note	Code
`VODIVIDE`	Chia phần	`Greedy -> Prefix Constraints`	-	prefix quota greedy; heap maintenance; pair reconstruction	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code

Math¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`KTHTERMOFLINEARLYRECURRENTSEQUENCE`	K-th Term of Linearly Recurrent Sequence	`Math -> Berlekamp-Massey / Kitamasa`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`DISCRETELOGARITHMMOD`	Discrete Logarithm Mod	`Math -> BSGS / Discrete Log`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`GENERALCHINESEREMAINDER`	Chinese Remainder Theorem (non-relatively prime moduli)	`Math -> Chinese Remainder And Linear Congruences`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`SUMOFDIVISORS`	Sum of Divisors	`Math -> Dirichlet Convolution / Prefix Sums Of Number-Theoretic Functions`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`CONVOLUTION`	Convolution	`Math -> FFT And NTT`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`POST2`	A cộng B version 2	`Math -> FFT And NTT`	-	convolution; digit aggregation; big integer addition	`medium`	VN SPOJ, ICPC-style	Map / Ladder / Tutorial	Note	Code
`SNIM`	S-Nim	`Math -> Game Theory / Sprague-Grundy`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`SYSTEMOFLINEAREQUATIONS`	System of Linear Equations	`Math -> Gaussian Elimination And Linear Algebra`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`COMMONDIVISORS`	Common Divisors	`Math -> GCD And LCM`	Math -> Number Theory Basics	divisor frequency scan; count multiples; maximize pair gcd	`medium`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`CRYPTKEY`	Chìa khóa mã số	`Math -> GCD And LCM`	Math -> Number Theory Basics	gcd-lcm closure; prime-power characterization; constructibility	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`EUCLIDPROBLEM`	Euclid Problem	`Math -> GCD And LCM`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`GCDONBLACKBOARD`	GCD on Blackboard	`Math -> GCD And LCM`	Math -> Number Theory Basics	prefix suffix gcd; remove one element; maximize array gcd	`medium`	AtCoder, Number theory	Map / Ladder / Tutorial	Note	Code
`THROWINGDICE`	Throwing Dice	`Math -> Linear Recurrence And Matrix Exponentiation`	-	linear recurrence; companion matrix; matrix exponentiation	`medium`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`BINOMIALCOEFFICIENTPRIMEMOD`	Binomial Coefficient (Prime Mod)	`Math -> Lucas Theorem And Large Binomial Mod Prime`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`SUMOFTOTIENTFUNCTION`	Sum of Totient Function	`Math -> Min_25 / Du Jiao`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`COUNTINGCOPRIMEPAIRS`	Counting Coprime Pairs	`Math -> Mobius And Multiplicative Counting`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`EXPONENTIATION`	Exponentiation	`Math -> Modular Arithmetic`	-	binary exponentiation; repeated squaring; modular fast power	`easy`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`EXPONENTIATION2`	Exponentiation II	`Math -> Modular Arithmetic`	-	binary exponentiation; fermat exponent reduction; zero exponent edge case	`medium`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`SQRTMOD`	Sqrt Mod	`Math -> Modular Square Root / Discrete Root`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`COUNTINGDIVISORS`	Counting Divisors	`Math -> Number Theory Basics`	Math -> GCD And LCM	divisor sieve; many queries preprocessing; divisor counting	`easy`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`LAMP`	Dàn đèn màu	`Math -> Number Theory Basics`	Math -> GCD And LCM; Combinatorics -> Inclusion-Exclusion	density formula; pairwise coprime products; big integer fractions	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`FACTORIZE`	Factorize	`Math -> Pollard-Rho`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`INVOFFORMALPOWERSERIES`	Inv of Formal Power Series	`Math -> Polynomial / Formal Power Series`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`PRIMITIVEROOT`	Primitive Root	`Math -> Primitive Root`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`DICEPROBABILITY`	Dice Probability	`Math -> Probability`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`XMAX`	XOR Maximization	`Math -> XOR Basis / Linear Basis`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code

Combinatorics¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`VOSFENCE`	Xay hang rao	`Combinatorics -> Bounded Compositions`	Combinatorics -> Counting Basics; Combinatorics -> Inclusion-Exclusion	bounded compositions; run decomposition; gap distribution	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`COUNTINGNECKLACES`	Counting Necklaces	`Combinatorics -> Burnside / Pólya / Group Actions`	Math -> Modular Arithmetic	burnside lemma; rotation symmetry; orbit counting	`hard`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`DISTRIBUTINGAPPLES`	Distributing Apples	`Combinatorics -> Counting Basics`	Math -> Modular Arithmetic	stars and bars; single binomial query; factorial precompute	`medium`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`PRIMEMULTIPLES`	Prime Multiples	`Combinatorics -> Inclusion-Exclusion`	Math -> Number Theory Basics	subset inclusion exclusion; overflow safe lcm product; count divisible numbers	`medium`	CSES, Mathematics	Map / Ladder / Tutorial	Note	Code
`VOITSORT`	Cây hoán vị	`Combinatorics -> Lexicographic Enumeration`	Graphs -> Trees	lexicographic enumeration; stack-sortability; cartesian tree view	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code

Strings¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`FINDINGPATTERNS`	Finding Patterns	`Strings -> Aho-Corasick`	Strings -> Trie	aho-corasick automaton; failure links; multi-pattern presence queries	`medium`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`DISTINCTPALINDROMICSUBSTRINGS`	Distinct Palindromic Substrings	`Strings -> Eertree / Palindromic Tree`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`FINDINGBORDERS`	Finding Borders	`Strings -> Hashing`	Advanced -> Randomized Algorithms	rolling hash; prefix-suffix equality; proper borders enumeration	`easy`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`STRINGMATCHING`	String Matching	`Strings -> KMP`	-	prefix function; border fallback; overlapping occurrence counting	`easy`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`LONGESTPALINDROME`	Longest Palindrome	`Strings -> Palindromes / Manacher`	-	manacher; odd/even centers; longest palindromic substring	`medium`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`REGEXMEMBERSHIP`	Regex Membership	`Strings -> Regular Expressions / Finite Automata`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`REPEATINGSUBSTRING`	Repeating Substring	`Strings -> Suffix Array And LCP`	-	suffix array doubling; kasai lcp; maximum adjacent lcp	`medium`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`DISTINCTSUBSTRINGS`	Distinct Substrings	`Strings -> Suffix Automaton`	Strings -> Suffix Array And LCP	suffix automaton construction; clone states; state contribution counting	`medium`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`PATTERNPOSITIONS`	Pattern Positions	`Strings -> Suffix Tree`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code
`WORDCOMBINATIONS`	Word Combinations	`Strings -> Trie`	-	trie plus dp; dictionary segmentation; suffix counting	`medium`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`FINDINGPERIODS`	Finding Periods	`Strings -> Z-Function`	Strings -> KMP	period detection; z function prefix matches; suffix prefix coverage	`easy`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code
`STRINGFUNCTIONS`	String Functions	`Strings -> Z-Function`	Strings -> KMP	z function; prefix function; prefix structure diagnostics	`easy`	CSES, String algorithms	Map / Ladder / Tutorial	Note	Code

Geometry¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`CONVEXHULL`	Convex Hull	`Geometry -> Convex Hull`	Geometry -> Vector And Orientation	andrew monotone chain; strict turn pop; boundary collinear points	`medium`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code
`BIGBROTHER`	Big Brother	`Geometry -> Half-Plane Intersection`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`MOGOHUREAIDOL`	Mogohu-Rea Idol	`Geometry -> Minkowski Sum`	-	-	`very-hard`	-	Map / Ladder / Tutorial	Note	Code
`CLOSESTPAIR`	Closest Pair	`Geometry -> Nearest Pair of Points`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`POINTINPOLYGON`	Point in Polygon	`Geometry -> Polygon Area And Point Location`	Geometry -> Vector And Orientation; Geometry -> Segment Intersection	ray casting parity; boundary classification; on segment test	`medium`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code
`POLYGONAREA`	Polygon Area	`Geometry -> Polygon Area And Point Location`	Geometry -> Vector And Orientation	shoelace formula; signed area accumulation; integer polygon area	`easy`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code
`PRAVO`	Tam giác vuông	`Geometry -> Right Triangles`	Advanced -> Algorithm Engineering; Geometry -> Counting Geometry; Geometry -> Vector And Orientation	count right triangles; normalized directions; perpendicular pairing	`medium`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`LINESEGMENTINTERSECTION`	Line Segment Intersection	`Geometry -> Segment Intersection`	Geometry -> Vector And Orientation	orientation test; on segment inclusion; collinear overlap handling	`easy`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code
`KINGDOMS`	KINGDOMS	`Geometry -> Sweep Line`	Graphs -> Trees; Geometry -> Polygon Area And Point Location	laminar regions; sweep events; containment tree	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`VOTELPH`	Bà Nà	`Geometry -> Sweep Line`	Geometry -> Polygon Area And Point Location	piecewise maximum; endpoint preprocessing; parabola envelopes	`hard`	VN SPOJ, ICPC-style	Map / Ladder / Tutorial	Note	Code
`POINTLOCATIONTEST`	Point Location Test	`Geometry -> Vector And Orientation`	-	cross product orientation; signed area test; turn classification	`easy`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code

Advanced¶

Code	Title	Primary	Also Fits	Pattern	Difficulty	Track	Learn	Note	Solution
`MINIMUMEUCLIDEANDISTANCE`	Minimum Euclidean Distance	`Advanced -> Algorithm Engineering`	Geometry -> Sweep Line	closest pair sweep line; active strip by x distance; ordered set by y	`hard`	CSES, Geometry	Map / Ladder / Tutorial	Note	Code
`BUILDTHEPERMUTATION`	Build the Permutation	`Advanced -> Constructive`	-	alternating core construction; local extrema counting; monotone leftover tail	`medium`	Codeforces, Constructive	Map / Ladder / Tutorial	Note	Code
`VMCOINS`	Trò chơi với những đồng xu	`Advanced -> Constructive`	Geometry -> Vector And Orientation	promise-driven constructive; translation matching; small residual search	`hard`	VN SPOJ, OI-style	Map / Ladder / Tutorial	Note	Code
`LINEARREGRESSIONGD`	Linear Regression Gradient Descent Benchmark	`Advanced -> Gradient Descent`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`PERCEPTRONCLASSIFICATION`	Perceptron Classification Benchmark	`Advanced -> Machine Learning Algorithms`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`PICKYOUROWNNIM`	Pick Your Own Nim	`Advanced -> Matroid Intersection`	-	-	`very-hard`	-	Map / Ladder / Tutorial	Note	Code
`MEETINTHEMIDDLE`	Meet in the Middle	`Advanced -> Meet-In-The-Middle`	-	-	`medium-hard`	-	Map / Ladder / Tutorial	Note	Code
`SKIRENTAL`	Ski Rental	`Advanced -> Online Algorithms`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`PARALLELPREFIXSUM`	Parallel Prefix Sum Benchmark	`Advanced -> Parallel Algorithms`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`DEUTSCHJOZSA`	Deutsch-Jozsa Oracle Benchmark	`Advanced -> Quantum Algorithms`	-	-	`medium`	-	Map / Ladder / Tutorial	Note	Code
`CHEESEIFYOUPLEASE`	Cheese, If You Please	`Advanced -> Simplex`	-	-	`hard`	-	Map / Ladder / Tutorial	Note	Code

Maintenance¶

Regenerate the catalog and topic maps with:

python3 scripts/generate_problem_catalog.py