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C# coding challenges

226 challenges you can solve in C#, from first loops to graphs, dynamic programming and machine learning. Write your code in the browser, run the tests instantly and get an AI review.

Easy · 134 Medium · 68 Hard · 24

Skills you'll practise: CountingDigit extractionString splitting2D listsArithmeticFormulasListsLoopsConditionsDivisibilityFloating pointGradient descent
  • Python · C++ · C#
  • Automated tests
  • AI code review
  • Community solutions
Programming
Programming fundamentalsFrom variables to recursion, for beginners
AI and machine learning
AI Learning HubNeural networks, ML and LLMs from scratch Neural networks from scratchNeurons, backpropagation and optimizers Machine learning from scratchRegression, classification and clustering Transformers and LLMs from scratchTokenizers, attention and text generation Classical AI and reinforcement learningSearch, games and reinforcement learning
226
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226 challenges
Easy

Roman Numeral Value

Convert a Roman numeral to a number.

You'll learn Symbol-to-value mapsSubtractive rules
BeginnerLookup-tablesStringsStudent-beginner
Python C++ C#
0 solved
No solutions yet
Hard

Matrix Chain Multiplication

Find the cheapest order to multiply a chain of matrices.

You'll learn Interval DPOptimization
AdvancedCompetitive-programmingDynamic-programming
Python C++ C#
0 solved
No solutions yet
Hard

Find Many Patterns in Text

For each requested pattern, decide whether it appears as a contiguous substring anywhere in the shared text.

You'll learn Substring searchPreprocessing
Pattern-matchingStringsTries
Python C++ C#
0 solved
No solutions yet
Easy

Character Frequency

Count how often each character appears.

You'll learn Frequency tablesCounting
BeginnerDictionariesStringsStudent-beginner
Python C++ C#
0 solved
No solutions yet
Medium

Recursive Power

Compute a power recursively by halving the exponent.

You'll learn Halving the exponentDivide and conquer
BeginnerLearning-pathRecursion
Python C++ C#
0 solved
No solutions yet
Medium

Count Grid Paths

Count routes across a rectangular grid using only right and down moves.

You'll learn Grid path countingBinomial coefficients
CombinatoricsDynamic-programming
Python C++ C#
0 solved
No solutions yet
Hard

Count Numbers With Distinct Neighbors

Count range values whose adjacent decimal digits are never equal.

You'll learn Digit DPCounting ranges
Dynamic-programmingNumbers
Python C++ C#
0 solved
No solutions yet
Easy

Multiplication Grid

Build a full multiplication table.

You'll learn 2D listsRow and column indexes
BeginnerLearning-pathNested-loops
Python C++ C#
0 solved
No solutions yet
Medium

A* Search on a Weighted Grid

Find the cheapest path across a grid of terrain costs with A*, the search algorithm behind game and robot pathfinding.

You'll learn A* searchHeuristics
GraphsGridsShortest-pathai
Python C++ C#
0 solved
No solutions yet
Easy

First Unique Character

Find the first character that appears only once.

You'll learn Hash mapsCounting
BeginnerDictionariesStringsStudent-beginner
Python C++ C#
0 solved
No solutions yet
Medium

Sum of Primes Below a Limit

Add all primes strictly below a limit.

You'll learn Sieve of EratosthenesSumming primes
Number-theorySieve
Python C++ C#
0 solved
No solutions yet
Hard

Maximum Project Rewards

Choose nonoverlapping projects to earn the largest total reward.

You'll learn Weighted schedulingDP with binary search
Dynamic-programmingScheduling
Python C++ C#
0 solved
No solutions yet
Medium

List Primes With a Sieve

Find primes up to a limit by marking composite multiples.

You'll learn Sieve of EratosthenesBoolean arrays
Number-theorySieve
Python C++ C#
0 solved
No solutions yet
Medium

Readability Grade

Estimate the school grade needed to read a text.

You'll learn Text analysisFormulas
BeginnerStringsStudent-beginnermath
Python C++ C#
0 solved
No solutions yet
Medium

Find Right-Triangle Triples

List all integer right triangles with a specified perimeter.

You'll learn EnumerationAvoiding duplicates
GeometryNumber-theory
Python C++ C#
0 solved
No solutions yet
Easy

Missing Number

Find the one number missing from 0..n.

You'll learn Arithmetic seriesSum difference trick
ArraysBeginnerStudent-beginnermath
Python C++ C#
0 solved
No solutions yet
Easy

Doubling Grains on a Chessboard

Calculate a square’s grain count and the total on all 64 squares.

You'll learn Powers of twoBig numbers
NumbersSequences
Python C++ C#
0 solved
No solutions yet
Easy

Sum Even Fibonacci Terms

Add the even Fibonacci terms that do not exceed a limit.

You'll learn Sequence generationFiltering
NumbersSequences
Python C++ C#
0 solved
No solutions yet

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