Hey Codeforces!
We're Codetree — a bunch of competitive programmers and former IOI/ICPC medalists who grew up grinding contests right here. This community shaped us, and now we want to give something back.
We've all seen the struggle:
- Grinding CF for interview prep but stuck at Grey/Green/Cyan despite putting in hours
- Can't seem to break out of DIV 3/4 contests
- No idea if you're actually getting better or just spinning wheels
- Watching others climb while you feel stuck
Been there. It sucks.
So we built something we wish we had years ago: Gap Check — a **completely free** tool that exposes the difference between what you think you know and what you actually know.
How it works:
- Choose your starting point:
- Just jump right in!
- Pick an algorithm tag you're studying
- Link a Leetcode problem you've been working on
- The Codeforces problem linking feature is currently under maintenance.
- Our adaptive testing engine (pretty sure it's the first of its kind in CP) will generate problems based on your speed and accuracy — with the familiar CP-style I/O format we all know
- Once your skill level converges, you'll get diagnosed across four categories: Missing Knowledge, Unstable Knowledge, Stable Knowledge, and Peak Performance
- We'll link you to free resources for exactly what you need to work on next
Sessions typically run 20 minutes, but can stretch to an hour for stronger coders — we'll keep pushing you with harder problems as long as you can handle them.
Back when I was comparing myself to Reds and feeling like garbage, having something that could actually pinpoint my weaknesses would have saved me months of random practice. Finding and fixing gaps one by one is what eventually leads to that sweet, sweet rating increase.
Try Gap Check here and see where you really stand.
We'd love your feedback on our analysis algorithm! As hardcore CFers, we know you'll spot any weaknesses in our approach, so please let us know what you think — especially if you find edges cases where our analysis breaks down.
For those who find joy in solving problems in the world through programming, Gap Check Team:
- Lead : GyojunYoun (ICPC World Final Gold-medalist, IOI Gold-medalist, IOI Silver-medalist)
- Members : plast, k5888200
Finally open! Good luck on codeforces.
Thank you!
I love plast.
I think plast loves you too.
Finally the game is over. Seems like it got more advanced than previous one!
Thank you so much! Give Gap Check one more try, and let us know if it's better than before.
plast orz
wow
Looks like an amazing tool! Is it possible to take the diagnostic test multiple times for free?
Thank you! Sure, you can test as many times as you want for free.
I totally relate to Watching others climb while you feel stuck... Thanks to Gap Check, I feel like I can reach GM. Thanks, Codetree!
We all feel stuck, and I can't wait to see how far you've come when you take Gap Check again after you become GM!
I hope this will take me back to CM...
I'm surprised to see how far it's come from when you first introduced it to me. I was still stuck in leetcode, but thanks for the update, I think I'll give CF a try soon.
Seems nice! I hope CF problem linking will be available soon.
In fact, the first phase of development is complete, but we're working on a few more things to perfect it. We'll update and let you know soon! Thank you so much!
If you have any questions about the test process or results, feel free to ask! Don't feel overwhelmed by the ratings. Gap Check is designed to cover all ratings.
Love the concept! I tried Gap Check, and it's pretty insightful. Keep it up!
I tried it, and on one problem I got like 5 compilation errors for simple syntax mistakes (I fixed them one at a time) — after fixing compile errors, the solution was correct. Your system still claimed I solved the problem with "great difficulty". Do you think it should work like this? I don't, but maybe I'm not the target audience, and writing code that compiles on the first try is something you want to value in the gap check. Just something to think about.
Thank you for your feedback! We'll think carefully about the points you've raised!
I got a buggy problem statement that asked to "select an even number of consecutive segments from the sequence $$$A$$$. ... From each selected segment, you can choose exactly half of the elements arbitrarily. ... Print the maximum total sum."
In the constraints, it mentioned a variable $$$K$$$ it hadn't mentioned before and in the first example it selected an odd number of segments.
So far, it's just this one that fell flat. The other problems it gave were pretty good at clarifying when needed.
Hello, this is CodeTree. We're sorry for the inconvenience caused by the error in the problem statement.
The issue has been fixed. We will work harder on reviewing our problems to prevent such incidents in the future.
I submitted a solution for this problem, then the page starts loading for infinite times and when it came back after I Reloaded the page, This was the scenario. I couldn't find the Editor.
Hello, this is CodeTree.
We sincerely apologize for the technical issue you experienced during the exam, where the page got stuck in an infinite loading state and the editor disappeared after submission.
Our development team is currently investigating this problem and will resolve it quickly. We will thoroughly check and improve our system to prevent such technical issues from occurring again.
We apologize once more for the inconvenience caused.
Thank you.
An unstable understanding of DFS, BFS for bitset suggests that while they can implement basic DFS or BFS algorithms, they struggle with efficiently managing visitations or devising optimal search strategies in complex graph structures, cycles, or disconnected components. To stabilize their understanding of DFS, BFS, it’s important to focus on solving multiple practice problems that involve appropriate use of recursion, loops, stacks, or queues, and tailoring DFS/BFS implementations and optimizations to fit various graph scenarios.bruh
Is the review correct?
I was attempting a problem on shortest paths and while writing dijkstra I ran my code to check whether it had any compilation errors , I did not output or return anything when I ran at first , The compiler got stuck at case 1 and did not allow me to submit again .
It would be a huge help if I could get the actual problem link so that I can submit my solution , can you please guide me through it if possible?
Hey _Artist__!
Thanks for letting us know. Can you provide a little more detail about the issue? It would be very helpful if you could DM me with your Codetree username.
idk if it's just me or this is a problem with the site because i can't go futher than this screen this page and i can't seem to move further no matter what i do
Thank you! CopperRoger Can you let me know what you tried?
If you didn't see the next button in a particular modal, it could be a resolution issue. Try zooming out your screen.