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:

1. 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.
2. 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
3. Once your skill level converges, you'll get diagnosed across four categories: Missing Knowledge, Unstable Knowledge, Stable Knowledge, and Peak Performance
4. 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