Train, teach and test coding and AI skills.

I'm learning to code
Lessons for beginners and practice problems up to interview level.
No account needed
I teach
A free textbook, assignments that grade themselves, and live quizzes.
Create a class Read the free textbook
I hire or run events
Coding assessments for hiring, hackathons and team training, with or without AI.
Set up an assessment How it works

Schools we've worked with

Learn to code in 17 languages, one short lesson at a time.
Practice on 9,000+ problems. Your code runs in the browser.
Hidden tests judge every submission, in solo practice or a live match.
Explore practice
Stuck? Rena gives you a hint, not the answer.
Race a friend on the same problem.
Build an app by telling the agent what to change. The preview updates as it edits.
See the files and diffs, review each change before you keep it, and export the project.
Explore Builder
Teach from a free textbook that comes with slides and labs.
Choose the AI help for each assignment: none, or hints that never write code.
Run a live coding quiz in class. Students join from their phones.
Multiple-choice and coding questions, with your screen and theirs in sync.
Explore Classroom
See every grade, each student's chat with Rena, and which code looks alike.
Code with an AI agent. Every prompt and every edit it makes is recorded.
Set No AI, Rena hints or a full agent for each task. A person makes the final decision.
Explore Assessments
Each score links to its evidence. Replay the session at that moment.

Learn to code in 17 languages, one short lesson at a time.
Practice on 9,000+ problems. Your code runs in the browser.
Hidden tests judge every submission, in solo practice or a live match.
Explore practice
Stuck? Rena gives you a hint, not the answer.
Race a friend on the same problem.
Build an app by telling the agent what to change. The preview updates as it edits.
See the files and diffs, review each change before you keep it, and export the project.
Explore Builder
Teach from a free textbook that comes with slides and labs.
Choose the AI help for each assignment: none, or hints that never write code.
Run a live coding quiz in class. Students join from their phones.
Multiple-choice and coding questions, with your screen and theirs in sync.
Explore Classroom
See every grade, each student's chat with Rena, and which code looks alike.
Code with an AI agent. Every prompt and every edit it makes is recorded.
Set No AI, Rena hints or a full agent for each task. A person makes the final decision.
Explore Assessments
Each score links to its evidence. Replay the session at that moment.

Company patterns

Practice what real interviews repeatedly test.

The patterns AlgoArena uses to prepare you for interviews at companies like these.

Accenture

MathTwo PointersRecursion

Infosys

BacktrackingRecursionBinary Search

IBM

Prefix SumBit ManipulationTwo Pointers

Visa

MatrixHeap (Priority Queue)Counting

Palantir

Graph TheoryBinary SearchSliding Window

J.P. Morgan

CountingHeap (Priority Queue)Greedy

Yelp

BacktrackingTrieRecursion

Intuit

Breadth-First SearchMatrixTree

EPAM Systems

Two PointersRecursionCounting

Flipkart

Graph TheoryHeap (Priority Queue)Breadth-First Search

Apple

TreeBreadth-First SearchDepth-First Search

Capital One

TrieSimulationMatrix

Snap

Graph TheoryBreadth-First SearchDepth-First Search

Oracle

TreeDepth-First SearchBreadth-First Search

Nvidia

RecursionLinked ListHeap (Priority Queue)

PayPal

CountingBinary SearchBacktracking

Coupang

RecursionHeap (Priority Queue)Breadth-First Search

Microsoft

TreeDepth-First SearchBacktracking

Snowflake

Graph TheoryDepth-First SearchTree

Wix

TreeRecursionDepth-First Search

Dropbox

BacktrackingGraph TheoryTrie

Palo Alto Networks

TreeLinked ListRecursion

Sharpened in the arena

Developers, founders, and CS students on practicing, competing, and getting ready for the interviews that count.

“I interviewed at a Series A startup and the format was basically what AlgoArena trains you for. They didn't just test algorithms, they tested how I think about product and how well I use AI to build. That's how interviews actually work now. When I worked at Tesla and big techs, you're expected to use AI, no questions asked. AlgoArena is the only one I've found that actually measures the skill that matters today: how well you work with AI, not without it.”

Jaehoon Son

Co-Founder, tryhermes.dev · CS & Math @ Swarthmore

“Working on AlgoArena was a great experience. The team is building something genuinely focused on improving how people learn and practice problem solving. I especially liked the clarity of vision and the speed at which ideas were being tested and shipped. It's a strong foundation, and I'm excited to see how it evolves.”

Yashwanth S

Founder, Startup Metric · CS @ ACE Engineering

“AlgoArena has transformed how I prepare for technical interviews. The platform's ranked 1v1 battles provide that real-world 'pressure' you can't get from standard coding sites. The AI-powered code analysis is a game-changer. It didn't just tell me my solution was wrong; it helped me understand the 'why' behind my logic errors. If you're serious about leveling up your DSA skills, this is the most interactive way to do it.”

Nawin M S

Backend Developer · CSE @ Velammal

“AlgoArena has helped me manage my time better in solving logic puzzles, and it's a much less stressful resource than LeetCode. The practice interview helps me get a gauge at what a coding interview experience might look like, and helps me prep without having to memorize exactly what to say. It helps me build the tools for a successful interview.”

Keyla Peralta

CS & Chinese @ Swarthmore

“AlgoArena has helped me develop my software development skills, and features such as the 1v1 battles have helped me develop problem solving skills under pressure. It has helped specifically with interview prep via the mock interviews with Rena and also with the constant skill building features.”

Isaac Lee

CS & Engineering @ Swarthmore

“Really love the interface! I'm using it to build an app.”

Sarika Saiyara

Bryn Mawr College

“I interviewed at a Series A startup and the format was basically what AlgoArena trains you for. They didn't just test algorithms, they tested how I think about product and how well I use AI to build. That's how interviews actually work now. When I worked at Tesla and big techs, you're expected to use AI, no questions asked. AlgoArena is the only one I've found that actually measures the skill that matters today: how well you work with AI, not without it.”

Jaehoon Son

Co-Founder, tryhermes.dev · CS & Math @ Swarthmore

“AlgoArena has transformed how I prepare for technical interviews. The platform's ranked 1v1 battles provide that real-world 'pressure' you can't get from standard coding sites. The AI-powered code analysis is a game-changer. It didn't just tell me my solution was wrong; it helped me understand the 'why' behind my logic errors. If you're serious about leveling up your DSA skills, this is the most interactive way to do it.”

Nawin M S

Backend Developer · CSE @ Velammal

“AlgoArena feels quite different from other platforms, and it's really exciting to explore. This platform is very new and makes coding feel like a game. Competing with others and solving problems within a time limit really helps improve our speed and prepares us better for coding interviews. I also like that the questions are presented in a different and interesting way. The gamified interface makes the whole experience much more enjoyable and keeps me motivated to practice more.”

Shaik Sariya Niyaz

Blockchain Intern, li2edu · CSE @ GPREC

“I really enjoyed problem solving on AlgoArena. Practicing in a competitive environment makes the DSA journey more engaging.”

Himanshu Singh

Java Backend Developer · MCA @ AKTU

“Legitimately stressful rushing to solve a LeetCode easy before your opponent. Fantastic interview prep. It definitely makes doing LeetCode problems more engaging and makes me try to finish them as fast as I can under pressure.”

Griffin Young

Principal Scientist, Schrödinger · CS @ Stanford

“I like how easy it is to jump into practice. The platform feels well organized, and the UI is great. Great work on building it!”

Yash Chaturvedi

Intern, DRDO · CSE @ MUJ

“What I like about the platform is that it gives me a good place to practice consistently instead of just solving random problems here and there. The problems have helped me think more about the logic and approach behind a solution rather than just trying to get the code working. Over time it has made me more comfortable with topics like recursion, sorting, arrays and other DSA concepts. I'd recommend it to other students who are trying to get better at problem solving and prepare themselves for coding interviews.”

Varun Shah

AI & Data Science @ DJSCE

“AlgoArena feels quite different from other platforms, and it's really exciting to explore. This platform is very new and makes coding feel like a game. Competing with others and solving problems within a time limit really helps improve our speed and prepares us better for coding interviews. I also like that the questions are presented in a different and interesting way. The gamified interface makes the whole experience much more enjoyable and keeps me motivated to practice more.”

Shaik Sariya Niyaz

Blockchain Intern, li2edu · CSE @ GPREC

“What I like about the platform is that it gives me a good place to practice consistently instead of just solving random problems here and there. The problems have helped me think more about the logic and approach behind a solution rather than just trying to get the code working. Over time it has made me more comfortable with topics like recursion, sorting, arrays and other DSA concepts. I'd recommend it to other students who are trying to get better at problem solving and prepare themselves for coding interviews.”

Varun Shah

AI & Data Science @ DJSCE