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Kotlin coding challenges
225 challenges you can solve in Kotlin, 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 · 67 Hard · 24
Skills you'll practise: CountingDigit extractionString splitting2D listsArithmeticFormulasListsLoopsConditionsDivisibilityFloating pointGradient descent
- Python · C++ · C#
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- Community solutions
- 226
- Challenges
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All challenges
Search by topic, language, or difficulty.
Medium
Two Nonattacking Knights
Count safe placements of two knights for each square board size.
You'll learn
Counting placementsAttack patterns
No solutions yet
Easy
Absolute Value Without abs
Compute an absolute value with a condition.
You'll learn
NegationNo built-ins
Medium
Number Spiral Lookup
Find a value by row and column in an expanding number spiral.
You'll learn
Math patternsCase analysis
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
No solutions yet
Easy
Activation Functions
Apply sigmoid, ReLU, Leaky ReLU or tanh to every value in a list.
You'll learn
SigmoidReLU and tanh
No solutions yet
Easy
DNA to RNA Transcription
Build an RNA string by replacing every DNA character with its partner.
You'll learn
Character mappingTranslation tables
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
No solutions yet
Easy
Count Handshakes
Count handshakes when every pair of people shakes hands once.
You'll learn
Counting pairsClosed formulas
No solutions yet
Easy
Palindrome String
Check whether text reads the same forwards and backwards.
You'll learn
Two pointersEarly exit
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
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
No solutions yet
Easy
Epsilon-Greedy Multi-Armed Bandit
Balance exploration and exploitation on a multi-armed bandit with epsilon-greedy action selection.
You'll learn
Explore vs exploitBandits
No solutions yet
Easy
Ticket Price by Age
Choose a cinema ticket price from the visitor's age.
You'll learn
Age rangesBoundary values
Medium
Perceptron Learning Algorithm
Train the original perceptron, which updates its weights only when it makes a mistake.
You'll learn
PerceptronOnline learning
No solutions yet
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