PythonPython 3.8.1 Judged
a, b = map(int, input().split())
print(a + b) The competitive coding platform, head to head
Practice Is Solitary,
Duels Aren’t
Stop solving problems in a vacuum. Face a real opponent, sharpen your instincts, and find out what you can do when the clock is running.
Free to play No card, no trial Ranked from your first duel
RANKED DUEL
14:12
Y
You1,428 rating
VS
nullbyte1,441 rating
N
MEDIUMSliding window
Ferry Queue
nullbyte is typingWriting solution…
-Problems in the catalog
-Topic chapters
8Languages judged
5Solves to get rated
The Grudge difference
Not Just Another
Practice Platform
Great developers are not built by collecting green checkmarks. They are built by making decisions with limited time, incomplete information and a little pressure.
See how a duel works01
Live Duels
Go head to head with a real developer on the same problem, picked near your rating.
Ranked 1v102Instant Feedback
Every submission runs against hidden tests the moment you send it. Know where you stand before the clock runs out.
03Earn Your Rating
Build a public track record that reflects how you actually perform under pressure.
Placed by 5 solves Simple by design
One Problem,
One Clear Winner
No setup. No endless scrolling. Just a focused challenge and the satisfaction of knowing you got better.
Start a duel- 01 / Get matched
Meet Your Opponent
Queue up and you are paired with someone near your rating, so every duel is a fair fight.
- 02 / Solve
Think Under Pressure
Same problem, same countdown. Pick your language, write your solution, watch the clock.
- 03 / Improve
Move Your Rating
Elo, not a solve count. Your first rating comes from 5 practice problems, and after that a win over someone far below you is worth almost nothing.
Built for your workflow
Your Language,
The Judge’s Version
Use the language you already know. Exact runtimes are published rather than implied, and the catalog is verified against these versions.
Live rankings
The Current
Top Contenders
The difference is clear
Duels Versus
Practising Alone
FeatureAlone Duel
A real opponent on the same problem
A clock you can actually lose to
A rating that moves with every result
Hidden tests, judged the moment you submit
Untimed practice when you want it
Your next opponent is waiting
Ready When
You Are
Free to play, and ranked from your very first duel.
Enter the arena Free to start · No card required Questions, answered
Good To Know
Yes. Every mode, every problem and ranked play are free. There is no paid tier and no card to enter.
Ranked duels pair you with someone near your rating, so the fight stays fair. Practice lets you pick any problem from the catalog, untimed and unrated.
No. Alongside DSA duels for CSE, there is a full ECE track: Verilog problems judged by a real simulator, predict-the-output questions, and courses on synthesis, static timing analysis, physical design, Tcl and Linux. Computer networks and system design are covered too.
No. The editor, the test runner and your results all live in the browser.
Yes. Create an invite link and send it to anyone; they join the same match directly.
An Elo-style system. A new account has no rating: solve 5 practice problems and your first rating is set from how fast and how cleanly you solved them. After that, each duel moves each player by an amount based on their own rating and the gap between you, and beating someone far below you is worth almost nothing.