Challenge Library
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.
Filter by type
Filter by difficulty
Popular topics
25 challenges matching your filters
Clear topic filter- Multiple ChoiceBeginner
SRP: finding the second reason to change
architecturesolidsrp - Multiple ChoiceIntermediate
OCP with real trade-offs
architecturesolidocp - Multiple ChoiceIntermediate
LSP: the invariant about preconditions
architecturesolidlsp - Multiple ChoiceIntermediate
ISP: fat interface vs client-specific ports
architecturesolidisp - Multiple ChoiceIntermediate
DIP: direction of dependency arrows
architecturesoliddiphexagonal - Multiple ChoiceHard
SOLID is not a checklist
architecturesolidover-abstraction - Multiple ChoiceIntermediate
OCP via data, not classes
architecturesolidocp - Multiple ChoiceBeginner
LSP and equals/hashCode contract
architecturesolidlsp - Multiple ChoiceIntermediate
DIP and the composition root
architecturesoliddip - Multiple ChoiceIntermediate
Tell, Don't Ask vs getters
architecturesolidencapsulation - Multiple ChoiceBeginner
Stable Dependencies Principle
coupling-metricsdependency-graphsolid - Multiple ChoiceHard
LSP violations in practice
lspsolidcollections - Multiple ChoiceBeginner
ISP and fat interfaces
ispsolidinterfaces - Code AnalysisIntermediate
Violated LSP with strengthened precondition
architecturesolidlsp - Code AnalysisIntermediate
Coupling leak: vendor type in domain
architecturesoliddiphexagonal - Code AnalysisBeginner
SRP: god class
architecturesolidsrp - Code AnalysisIntermediate
Strategy gone wrong: enum switch
architecturesolidocp - Code AnalysisBeginner
LSP: equals/hashCode mismatch
architecturesolidlsp - Code AnalysisBeginner
ISP in a module interface
architecturesolidisp - Code AnalysisIntermediate
LSP: widening (not narrowing) can also break
architecturesolidlsp - Code AnalysisBeginner
Dependency inversion missing in service
architecturesoliddip - Code AnalysisIntermediate
Analyze: LSP behavioral subtyping break
lspsolidsubtyping - Code AnalysisIntermediate
Analyze: SRP multiple reasons to change
srpsolidcohesion - Code AnalysisHard
Violated principle in subclass override
lspsolidcode-analysis - Code AnalysisIntermediate
Fat interface / ISP violation
ispsolidcode-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.