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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
Medium

Raise a Number to a Fractional Power

Raise a positive real number to a rational exponent.

You'll learn Roots and powersFloating point
Fractionsmath
Python C++ C#
0 solved
No solutions yet
Easy

Armstrong Number

Check whether a number equals the sum of its digits raised to the digit count.

You'll learn Digit extractionPowers
BeginnerNumbersStudent-beginner
Python C++ C#
0 solved
No solutions yet
Medium

Tree Diameter

A tree is a connected undirected graph with no cycles.

You'll learn Double BFSAdjacency lists
GraphsTrees
Python C++ C#
0 solved
No solutions yet
Easy

Power by Repeated Multiplication

Raise a number to a power with a loop.

You'll learn Running productZero exponent
BeginnerLearning-pathLoops
Python C++ C#
0 solved
No solutions yet
Easy

Sum of Odd Numbers

Add every odd number up to a limit.

You'll learn For loopsAccumulators
BeginnerLearning-pathLoops
Python C++ C#
0 solved
No solutions yet
Medium

Count Coin Combinations

Count ways to make an amount with unlimited coins of specified denominations.

You'll learn Unbounded knapsackCounting combinations
CombinatoricsDynamic-programming
Python C++ C#
0 solved
No solutions yet
Medium

Exact Fraction Arithmetic

Perform fraction operations and return a reduced fraction.

You'll learn GCD reductionSign normalization
Fractionsmath
Python C++ C#
0 solved
No solutions yet
Medium

Count Dice Sequences

Count ordered die-roll sequences with a given total.

You'll learn RecurrencesModular counting
CombinatoricsDynamic-programming
Python C++ C#
0 solved
No solutions yet
Medium

One Generation of a Genetic Algorithm

Breed the next generation of bit strings with tournament selection, single-point crossover and mutation.

You'll learn Genetic algorithmsEvolutionary search
OptimizationSimulationai
Python C++ C#
0 solved
No solutions yet
Medium

Factory Production Time

Find the earliest time parallel machines can finish a target number of items.

You'll learn Binary search on answerMonotonic checks
AlgorithmsBinary-search
Python C++ C#
0 solved
No solutions yet
Medium

Value Iteration

Compute how valuable each state of a Markov decision process is by repeatedly applying the Bellman optimality update.

You'll learn Bellman equationMDPs
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Palindrome String

Check whether text reads the same forwards and backwards.

You'll learn Two pointersEarly exit
BeginnerStringsStudent-beginner
Python C++ C#
0 solved
No solutions yet
Medium

Smallest Missing Coin Sum

Find the first positive amount that cannot be made from the available coins.

You'll learn Reachable sumsSorting first
ArraysGreedy
Python C++ C#
0 solved
No solutions yet
Medium

Robot Command Simulator

Move a robot using L (turn left 90 degrees), R (turn right 90 degrees), and A (advance one step).

You'll learn Direction vectorsCommand processing
SimulationState-machines
Python C++ C#
0 solved
No solutions yet
Medium

Q-Learning Updates

Apply the Q-learning update to a stream of experiences and watch rewards flow back to earlier states.

You'll learn Q-learningDiscounted rewards
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Multiplication Table Row

List the first multiples of a number.

You'll learn MultiplesBuilding lists
BeginnerLearning-pathLoops
Python C++ C#
0 solved
No solutions yet
Medium

Perceptron Learning Algorithm

Train the original perceptron, which updates its weights only when it makes a mistake.

You'll learn PerceptronOnline learning
Neural networksaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Make an Array Nondecreasing

Find the fewest increments needed so each value is at least the previous one.

You'll learn Greedy fixesRunning maximum
ArraysGreedy
Python C++ C#
0 solved
No solutions yet

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