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213 tasks across the Municipal, Regional, and National rounds (2009–2026), plus 4 previously featured problems. 146 tasks have independently written English summaries, analyses, and C++17 solutions; the remaining entries link to Arena. Topic tags are from Arena or our reviewed explanations. Difficulty labels are learning estimates, not official ratings.

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RoundYearContent

Graphs38

BFS & shortest paths 8

BFS with state masks 1

Connected Components 1

Cycle detection 1

Cycle Equations 1

DFS & reachability 5

Dijkstra & weighted routes 7

Directed Bfs 1

DSU & connectivity 2

Grid Distance 1

Lowest common ancestor 1

Minimum spanning trees 1

Multi Source Bfs 1

Permutation cycles & weighted swaps 1

Spanning trees 1

Strongly Connected Components 1

Topological Order 1

Trees & DAGs 3

Dynamic Programming42

Acyclic State Dp 1

Bitmask Dp 1

Combinatorial Dp 2

Combinatorial DP 1

Counting Dp 1

Digit Dp 1

Dynamic programming 14

Dynamic programming on grids 1

Interval Dp 3

Interval dynamic programming 1

Knapsack 1

Layered Dp 1

Linear Dp 3

Multiple Pointer Generation 1

Ordered States 1

Polynomial Dp 1

Sequence Dp 1

Sliding Window Dp 1

String Segmentation 1

Subsequence Counting 1

Subset Dp 1

Subset Sum 2

Unbounded Knapsack 1

Greedy Algorithms14

Coverage 1

Digit Construction 1

Enumeration And Packing 1

Greedy algorithms 3

Greedy digit construction 1

Greedy selection & counting 1

Interval Costs 1

Interval Expansion 1

Monotonic Stack 1

Permutations 1

Sorting And Binary Search 1

Sorting Greedy 1

Arrays & Sorting20

Distance Transform 1

Frequency Counting 1

Interval Merging 2

Matrices & grids 1

Matrix Traversal 2

Prefix Sums 2

Reverse Difference Arrays 1

Run Length Counting 1

Sorting 1

Sweep Line 2

Two pointers & sliding windows 6

Search & Enumeration11

Backtracking 2

Binary search 1

Binary Search 1

Binary Search Answer 2

Binary Search On Answer 1

Binary search on the answer 2

Enumeration & brute force 2

Strings9

Coordinate Compression 1

Hashing 1

Implicit Strings 1

Overlap 1

Palindromes 1

Prefix Function 1

Prefix Sums 1

Strings 1

Subsequence recognition 1

Mathematics37

Big integers 1

Big Integers 2

Binary Representation 1

Binomial Coefficients 1

Bitwise Xor 1

Combinatorial unranking 1

Combinatorics 3

Compressed Gcd States 1

Digit arithmetic 1

Digit Counting 1

Divisibility 1

Divisors 3

Extended Euclid 1

Fractions 1

Gcd And Divisors 1

Information bounds & binary codes 1

Integer Powers 1

Invariants 1

Mathematics 2

Modular Arithmetic 1

Number theory 1

Numeral Systems 1

Prefix Formulas 1

Prime Factorization 1

Prime factors & sliding windows 1

Prime Sieve 3

Rational Arithmetic 1

Recurrences 1

Sum Identities 1

Geometry8

Angles 1

Circular Intervals 1

Coordinate Geometry 1

Intervals 1

Polygon Clipping 1

Sorting Faces 1

Sweep Line 2

Data Structures8

Monotonic Queue 1

Ordered Sets 1

Sets 1

Stacks & expressions 5

Implementation8

Bit manipulation & decoding 1

Counting 1

Grid Simulation 1

Interpreters & memoization 1

Ranked Choice Simulation 1

Simulation 3

Topic Not Yet Reviewed22

Awaiting topic review 22

Try the problem yourself before reading the analysis. Every solution uses standard C++17 headers.

GROUP C2009 · Not assessedMatrices & grids

diag

National Olympiad — Regional round

Submission name: diag.cpp

Source catalogue entry

This task is indexed from Arena’s Group C Olympiad archive. An English explanation and verified C++17 solution have not been added yet.

Topic labels come from Arena’s catalogue. Difficulty has not yet been assessed.

Catalogue topics

Matrices & grids

Use the source link below to open the official problem.

Source: Arena Olimpiici ↗

Real problems.Your next challenge.

diag

Source catalogue entry

Catalogue topics

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Real problems.
Your next challenge.