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Python coding challenges

226 challenges you can solve in Python, 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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  • AI code review
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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
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
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
Easy

Letter Grade

Turn a test score into a letter grade.

You'll learn if/elif chainsRanges
BeginnerConditionsLearning-path
Python C++ C#
0 solved
No solutions yet
Medium

Number Spiral Lookup

Find a value by row and column in an expanding number spiral.

You'll learn Math patternsCase analysis
Patternsmath
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
Easy

Median of a List

Find the middle value of a list after sorting.

You'll learn SortingStatistics
Arraysmath
Python C++ C#
0 solved
No solutions yet
Easy

Count Handshakes

Count handshakes when every pair of people shakes hands once.

You'll learn Counting pairsClosed formulas
Combinatoricsmath
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
Easy

Array Maximum

Find the largest value in a list.

You'll learn Tracking a maximumSingle pass
ArraysBeginnerStudent-beginner
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

Acronym Generator

Create an acronym from the first letter of every word, in uppercase.

You'll learn String parsingWord splitting
ParsingStrings
Python C++ C#
0 solved
No solutions yet
Easy

Triangle Classification

Classify three side lengths as invalid, equilateral, isosceles, or scalene.

You'll learn Triangle inequalityOrdering conditions
ConditionsGeometry
Python C++ C#
0 solved
No solutions yet
Easy

Pangram Check

A pangram contains every English letter at least once.

You'll learn Letter setsCase normalization
SetsStrings
Python C++ C#
0 solved
No solutions yet
Medium

Nearest Smaller Value to the Left

For each number, find the closest earlier position containing a strictly smaller number.

You'll learn Monotonic stackLinear time
ArraysStacks
Python C++ C#
0 solved
No solutions yet
Easy

Largest of Three

Pick the largest of three numbers without a built-in max.

You'll learn ComparisonsCombining conditions
BeginnerConditionsLearning-path
Python C++ C#
0 solved
No solutions yet
Easy

Count Positive Numbers

Count the values greater than zero in a list.

You'll learn ListsCounting
ArraysBeginnerLearning-path
Python C++ C#
0 solved
No solutions yet
Easy

Absolute Value Without abs

Compute an absolute value with a condition.

You'll learn NegationNo built-ins
BeginnerConditionsLearning-path
Python C++ C#
0 solved
No solutions yet
Easy

First Negative Index

Find where the first negative number appears.

You'll learn Linear searchEarly return
ArraysBeginnerLearning-path
Python C++ C#
0 solved
No solutions yet

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