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Coding Challenges

5,893 curated questions across every arena — browse by topic, then jump into a live 3-minute battle to put them to the test.

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63 challenges matching your filters

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Code AnalysisIntermediate
Macro Expansion Trap
code-analysisClanguage
Code AnalysisIntermediate
Post-increment Loop
code-analysisClanguage
Code AnalysisIntermediate
Pointer Arithmetic
code-analysisClanguage
Code AnalysisIntermediate
String Literal Length
code-analysisClanguage
Code AnalysisIntermediate
Ternary Operator
code-analysisClanguage
Code AnalysisIntermediate
Deleting derived through base pointer
cppvirtualdestructorundefined-behavior
Code AnalysisIntermediate
Capture by reference outliving scope
cpplambdacapturedangling
Code AnalysisIntermediate
Dangling reference in std::async
cppasynclambdacapture
Code AnalysisIntermediate
Return local by value
cpprvoreturncode-analysis
Code AnalysisIntermediate
Lambda returning reference to by-value capture
cpplambdadanglingreferences
Code AnalysisIntermediate
Virtual call during destruction
cppvirtualdestructorcode-analysis
Code AnalysisIntermediate
unordered_map pointer survives rehash
cppstlunordered_mapiterator-invalidation
Code AnalysisIntermediate
Reference to vector element across growth
cppstlvectordangling
Code AnalysisIntermediate
Brace init narrowing error
cppaggregate-initnarrowingcode-analysis
Code AnalysisIntermediate
const member mutating through pointer
cppconst-correctnesspointersgotcha
Code AnalysisIntermediate
new[] / delete mismatch
cppundefined-behaviornew-deletecode-analysis
Code AnalysisIntermediate
Range-for over returning-by-value container
cpprange-forlifetimecode-analysis
Code AnalysisIntermediate
Two-mutex lock-order deadlock
cppthreadingdeadlockmutex
Code AnalysisIntermediate
volatile increment not atomic
cppatomicsvolatiledata-race
Code AnalysisIntermediate
Detached thread using this
cppthreadingdanglinglambda
Code AnalysisIntermediate
std::thread destructor terminate
cppthreadingstd-threadcode-analysis
Code AnalysisIntermediate
sizeof object with vptr
cppsizeofvtablecode-analysis
Code AnalysisIntermediate
constexpr used as array bound
cppconstexprarraycode-analysis
Code AnalysisIntermediate
vector uses copy when move may throw
cppexception-safetynoexceptvector
Code AnalysisIntermediate
Infinite loop optimized away
cppatomicsundefined-behavioroptimization
Code AnalysisIntermediate
Calling empty std::function
cppstd-functioncode-analysis
Code AnalysisIntermediate
No implicit void* conversion
cpptypingvoid-pointercode-analysis
Code AnalysisIntermediate
atomic double CAS loop output
atomicsfloating-pointcode-analysis
Code AnalysisIntermediate
flat_map sort key output
flat_mapcontainerscode-analysis
Code AnalysisIntermediate
structured binding reference output
structured-bindingsrange-forcode-analysis
Code AnalysisIntermediate
pimpl unique_ptr inline dtor output
pimplunique_ptrincomplete-typecode-analysis
Code AnalysisIntermediate
to_chars buffer too small output
to_charsnumericcode-analysis
Code AnalysisIntermediate
Close Channel Read
code-analysisGolanguage
Code AnalysisIntermediate
Defer LIFO
code-analysisGolanguage
Code AnalysisIntermediate
Switch No Expression
code-analysisGolanguage
Code AnalysisIntermediate
Async forEach
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
Closure var Loop
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
Float Equality
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
Microtask vs Task
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
null vs undefined
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
This Lost Binding
code-analysisJavaScriptlanguage
Code AnalysisIntermediate
Generator Exhaustion
code-analysisPythonlanguage
Code AnalysisIntermediate
Lambda Late Binding
code-analysisPythonlanguage
Code AnalysisIntermediate
List Comp Scope
code-analysisPythonlanguage
Code AnalysisIntermediate
nonlocal Keyword
code-analysisPythonlanguage
Code AnalysisIntermediate
Try Else Finally Order
code-analysisPythonlanguage
Code AnalysisIntermediate
Tuple Mutable Item
code-analysisPythonlanguage
Code AnalysisIntermediate
Missing transactional outbox
outboxreliabilitycode-analysis
Code AnalysisIntermediate
Sync engine conflict handling
sync-engineconflict-resolutioncode-analysis
Code AnalysisIntermediate
DIP violation via direct SDK import
dipports-and-adapterscode-analysis
Code AnalysisIntermediate
Fat interface / ISP violation
ispsolidcode-analysis
Code AnalysisIntermediate
Composition over inheritance refactor
compositioninheritancecode-analysis
Code AnalysisIntermediate
Template method wrong fit
template-methodstrategycode-analysis
Code AnalysisIntermediate
Strategy vs state selection
statestrategycode-analysis
Code AnalysisIntermediate
Visitor for business rules
visitorpatternscode-analysis
Code AnalysisIntermediate
Durable execution vs retries
durable-executionworkflow-enginecode-analysis
Code AnalysisIntermediate
Data contract for analytics eventing
data-contractseventingcode-analysis
Code AnalysisIntermediate
Which Evolution Strategy Fits
expand-contractschema-evolutioncode-analysis
Code AnalysisIntermediate
Which Consistency Flaw
sagacompensationcode-analysis
Code AnalysisIntermediate
Which Backpressure Gap
backpressureoverloadcode-analysis

Practice now, dominate the arena

Every challenge here is drawn from the live Code Royale pool. Review a question, then head to the arena to answer under pressure against a real opponent — 3-minute matches, Elo ranking, and badge tiers on the line.

Coding Challenges

Macro Expansion Trap

Post-increment Loop

Pointer Arithmetic

String Literal Length

Ternary Operator

Deleting derived through base pointer

Capture by reference outliving scope

Dangling reference in std::async

Return local by value

Lambda returning reference to by-value capture

Virtual call during destruction

unordered_map pointer survives rehash

Reference to vector element across growth

Brace init narrowing error

const member mutating through pointer

new[] / delete mismatch

Range-for over returning-by-value container

Two-mutex lock-order deadlock

volatile increment not atomic

Detached thread using this

std::thread destructor terminate

sizeof object with vptr

constexpr used as array bound

vector uses copy when move may throw

Infinite loop optimized away

Calling empty std::function

No implicit void* conversion

atomic double CAS loop output

flat_map sort key output

structured binding reference output

pimpl unique_ptr inline dtor output

to_chars buffer too small output

Close Channel Read

Defer LIFO

Switch No Expression

Async forEach

Closure var Loop

Float Equality

Microtask vs Task

null vs undefined

This Lost Binding

Generator Exhaustion

Lambda Late Binding

List Comp Scope

nonlocal Keyword

Try Else Finally Order

Tuple Mutable Item

Missing transactional outbox

Sync engine conflict handling

DIP violation via direct SDK import

Fat interface / ISP violation

Composition over inheritance refactor

Template method wrong fit

Strategy vs state selection

Visitor for business rules

Durable execution vs retries

Data contract for analytics eventing

Which Evolution Strategy Fits

Which Consistency Flaw

Which Backpressure Gap

Practice now, dominate the arena