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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
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226 challenges
Easy

Z-Score Standardization

Center a feature at 0 and scale it to a standard deviation of 1.

You'll learn StandardizationMean and std dev
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Softmax Function

Turn raw scores into probabilities that add up to 1, without overflowing on large values.

You'll learn SoftmaxNumerical stability
aimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Causal (Masked) Self-Attention

Implement the masked attention GPT models use, where each token can only look at itself and earlier tokens.

You'll learn Masked attentionGPT models
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Word Tokenizer and Vocabulary

Split text into lowercase words and build a vocabulary sorted by frequency, the first step of any language model.

You'll learn TokenizationVocabulary building
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Matrix Multiplication

Multiply two matrices, the operation behind every layer of a neural network.

You'll learn MatricesLinear algebra
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Smallest Digit

Find the smallest decimal digit of a positive integer.

You'll learn Digit extractionTracking a minimum
Beginner
Python C++ C#
0 solved
No solutions yet
Easy

Factorial

Multiply all positive integers up to n.

You'll learn LoopsRunning product
Beginner
Python C++ C#
0 solved
No solutions yet
Easy

Largest Digit

Find the largest decimal digit of a positive integer.

You'll learn Digit extractionTracking a maximum
Beginner
Python C++ C#
0 solved
No solutions yet
Medium

Information Gain

Compute how much splitting on a feature reduces entropy, the criterion behind ID3 decision trees.

You'll learn EntropyDecision trees
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Sum of Digits

Add up the decimal digits of a positive integer.

You'll learn Modulo and divisionWhile loops
Beginner
Python C++ C#
0 solved
No solutions yet
Easy

Triangular Number

Add the integers from 1 through n.

You'll learn LoopsArithmetic series
Beginner
Python C++ C#
0 solved
No solutions yet
Medium

K-Nearest Neighbors Classifier

Predict a label by majority vote of the k closest training points.

You'll learn KNNDistance metrics
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Dot Product of Two Vectors

Multiply two vectors element by element and add the results: the core operation of every neuron.

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

Square a Number

Multiply an integer by itself.

You'll learn FunctionsArithmetic
Beginner
Python C++ C#
0 solved
No solutions yet
Easy

Reverse a Number

Reverse the decimal digits of a positive integer.

You'll learn Digit extractionBuilding numbers
Beginner
Python C++ C#
0 solved
No solutions yet
Easy

Count Digits

Count the decimal digits of a positive integer.

You'll learn Integer divisionCounting loops
Beginner
Python C++ C#
0 solved
No solutions yet
Hard

Scaled Dot-Product Attention

Implement the attention operation at the heart of Transformers and large language models.

You'll learn AttentionTransformers
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Checkout Facade

Hide stock checks and price totals behind one simple checkout call.

You'll learn Facade patternValidation
ArraysDesign patternsSimulation
Python C++ C#
0 solved
No solutions yet

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