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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#
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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
Medium

Gradients of a Single Neuron

Use the chain rule to find how the loss changes with each weight and the bias of a sigmoid neuron.

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

Sum an Array

Add up all values in a list.

You'll learn AccumulatorsEmpty-list cases
ArraysBeginnerStudent-beginner
Python C++ C#
0 solved
No solutions yet
Easy

Difference of Squares

Subtract the sum of squares from the square of the sum.

You'll learn FormulasArithmetic
Beginnermath
Python C++ C#
0 solved
No solutions yet
Easy

Loss Functions: MSE, MAE and Cross-Entropy

Measure how wrong a model's predictions are with mean squared error, mean absolute error or binary cross-entropy.

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

Single Artificial Neuron

Compute the output of one neuron: weighted sum of the inputs plus a bias, passed through sigmoid.

You'll learn NeuronsWeighted sums
Neural networksaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Layer Normalization

Normalize each row to zero mean and unit variance, then scale and shift it, as every Transformer block does.

You'll learn Layer normTransformers
Neural networksaimachine learning
Python C++ C#
0 solved
No solutions yet
Hard

Backpropagation in a Two-Layer Network

Compute every weight and bias gradient of a network with one sigmoid hidden layer and one sigmoid output.

You'll learn BackpropagationChain rule
Neural networksaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Digital Root

Sum the digits repeatedly until one digit remains.

You'll learn Nested loopsDigit sums
Algorithms
Python C++ C#
0 solved
No solutions yet
Easy

Derivatives of Activation Functions

Compute the derivative of sigmoid, ReLU, Leaky ReLU or tanh at each value, the slopes backpropagation needs.

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

Digit Power Sum

Add each digit raised to its position from the left.

You'll learn Digit extractionPowersLoops
Algorithms
Python C++ C#
0 solved
No solutions yet
Easy

Markov Chain State Distribution

Propagate a probability distribution through a Markov chain's transition matrix for a number of steps.

You'll learn Markov chainsProbability
Simulationaimath
Python C++ C#
0 solved
No solutions yet
Medium

Dense Layer Forward Pass

Compute the outputs of a fully connected layer of neurons with a choice of activation.

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

Chess Square Color

Determine the color of a square on an 8 by 8 board.

You'll learn CoordinatesParity
Beginnermath
Python C++ C#
0 solved
No solutions yet
Medium

Minimax Tic-Tac-Toe

Pick the perfect tic-tac-toe move by searching the whole game tree with minimax.

You'll learn MinimaxGame trees
Recursionai
Python C++ C#
0 solved
No solutions yet
Medium

Mini-Batch Gradient Descent

Train a linear model by updating the weights after every small batch of samples instead of the whole dataset.

You'll learn Mini-batchesGradient descent
Neural networksaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Hours, Minutes, and Seconds

Convert a duration in seconds to a compact readable string.

You'll learn Time unitsString formatting
Beginnermath
Python C++ C#
0 solved
No solutions yet
Hard

Multi-Head Self-Attention

Project the input into queries, keys and values, run attention in several heads in parallel, and combine them.

You'll learn Multi-head attentionMatrix projections
aimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Gradient Descent with Momentum

Apply momentum updates, which keep part of the previous step so training speeds up along consistent directions.

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

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