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
9 challenges matching your filters
Clear topic filter- Multiple ChoiceIntermediate
LSP: the invariant about preconditions
architecturesolidlsp - Multiple ChoiceBeginner
LSP and equals/hashCode contract
architecturesolidlsp - Multiple ChoiceHard
LSP violations in practice
lspsolidcollections - Code AnalysisIntermediate
Violated LSP with strengthened precondition
architecturesolidlsp - Code AnalysisBeginner
LSP: equals/hashCode mismatch
architecturesolidlsp - Code AnalysisIntermediate
Wrong abstraction via forced hierarchy
architectureover-abstractionlsp - Code AnalysisIntermediate
LSP: widening (not narrowing) can also break
architecturesolidlsp - Code AnalysisIntermediate
Analyze: LSP behavioral subtyping break
lspsolidsubtyping - Code AnalysisHard
Violated principle in subclass override
lspsolidcode-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.