Efibb CodeArena
Prepare for coding interviews—and prove real engineering ability.
Practice algorithms, SQL, debugging, testing, secure coding, APIs, cloud, DevOps, and system design through original challenges connected to pathways and evidence.
Original Efibb challenge catalogLanguage-extensible adaptersEncrypted source at restIsolated runner required
Interview and engineering tracks
Build depth, not just streaks.
Strings & Parsing
12 challengesOpen track →Stacks & Queues
12 challengesOpen track →Trees & Graphs
12 challengesOpen track →Dynamic Programming
12 challengesOpen track →SQL & Data
12 challengesOpen track →Debugging & Testing
12 challengesOpen track →Backend & APIs
12 challengesOpen track →Frontend & Accessibility
12 challengesOpen track →Cloud & DevOps
12 challengesOpen track →Secure Coding
12 challengesOpen track →System Design
12 challengesOpen track →Language-extensible
Choose the language you want to interview in.
Python3.13 • editor readyJavaScript22 • editor readyTypeScript5.8 • editor readyJava21 • editor readyC++14 • editor readyC#9 • editor readyGo1.24 • editor readyRust1.85 • editor readyKotlin2.1 • editor readySwift6.0 • editor readyPHP8.4 • editor readyRuby3.4 • editor readySQL17 • editor readyBash5.2 • editor ready
Featured challenges
Start solving.
easyArrays & Hashing
Event Frequency Ledger
Summarize repeated event codes for a telemetry batch.
Practice challengeeasyArrays & Hashing
Scholarship Tag Counter
Count normalized scholarship tags for discovery ranking.
Practice challengemediumArrays & Hashing
Inventory Signal Index
Build a stable count index for marketplace inventory signals.
Practice challengehardArrays & Hashing
Assessment Answer Histogram
Count answer choices without losing case-sensitive distinctions.
Practice challengeeasyArrays & Hashing
Application Fee Pair
Find the earliest two fees that exactly match a budget.
Practice challengeeasyArrays & Hashing
Capacity Pair Finder
Locate the first compatible capacity pair for a deployment target.
Practice challengemediumArrays & Hashing
Course Credit Pair
Find two course-credit values that reach a graduation requirement.
Practice challengehardArrays & Hashing
Travel Cost Pair
Find two quoted costs that use the remaining travel allowance.
Practice challengeeasyArrays & Hashing
Deadline Interval Merge
Normalize overlapping admissions deadline windows.
Practice challengeeasyArrays & Hashing
Maintenance Window Merge
Merge overlapping platform maintenance periods.
Practice challengemediumArrays & Hashing
Interview Availability Merge
Consolidate overlapping interview availability blocks.
Practice challengehardArrays & Hashing
Visa Appointment Window Merge
Canonicalize overlapping appointment windows.
Practice challenge