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Arrays coding challenges

Practise arrays with 31 coding challenges, from easy to hard. Every challenge runs in your browser with instant tests, an AI review of your code and community solutions to compare.

Easy · 27 Medium · 3 Hard · 1

Skills you'll practise: ListsSingle passSortingTwo pointers2D arrays2D lists8-neighbor checksAccumulatorsAmortised costArithmetic seriesArray indexingAsync/await
  • Python · C++ · C#
  • Automated tests
  • AI code review
  • Community solutions
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31 challenges
Easy

Running Sum

Replace each value with the total so far.

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

Pascal’s Triangle

Build rows by adding neighboring entries from the previous row.

You'll learn 2D listsBuilding from previous rows
ArraysCombinatorics
Python C++ C#
0 solved
No solutions yet
Easy

Array Average

Compute the average of a list of numbers.

You'll learn Sum and countFloat division
ArraysBeginnerStudent-beginner
Python C++ C#
0 solved
No solutions yet
Easy

Move Zeroes

Move every zero to the end while keeping the other order.

You'll learn Two pointersIn-place updates
ArraysBeginnerStudent-beginner
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

Rotate Array

Rotate a list to the right by some steps.

You'll learn Array indexingModulo
ArraysBeginnerStudent-beginner
Python C++ C#
0 solved
No solutions yet
Easy

Flatten a 2D Array

Combine the rows of a 2D integer array into one array.

You'll learn 2D arraysNested loops
ArraysLoops
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
Easy

Join Customers and Orders

Join customers with their orders like a LINQ Join and report each customer's total spend.

You'll learn LINQ JoinGrouping
ArraysSorting
Python C++ C#
0 solved
No solutions yet
Easy

Growing a Dynamic Array

Simulate how a dynamic array doubles its capacity and count the reallocations and copied elements.

You'll learn Dynamic arraysAmortised cost
ArraysSimulationmath
Python C++ C#
0 solved
No solutions yet
Easy

WhenAll Total Time

Find how long a program takes when each group of tasks runs together with Task.WhenAll and groups run one after another.

You'll learn Async/awaitTask.WhenAll
ArraysBeginner
C++ Python C#
0 solved
No solutions yet
Easy

Split a List Into Chunks

Cut a list into consecutive groups of a fixed size, with a shorter last group if needed.

You'll learn SlicingBatching
ArraysBeginner
Python C++ C#
0 solved
No solutions yet
Easy

Sort by a Chosen Key

Sort people by name or by age with a comparer chosen at run time, breaking ties consistently.

You'll learn ComparersSorting
ArraysSorting
Python C++ C#
0 solved
No solutions yet

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