Hi Codeforces!

A small update to our previous posts about VoidHub.

I, together with AdhamAfterMidnight, have added a new problem source to the platform: VH (VoidHub).

Hi Codeforces!

About seven weeks ago, AdhamAfterMidnight and I shared VoidHub, a project we started while preparing for the ECPC.

The main idea was simple: make regular practice feel less repetitive. Invite a friend, enter a live 1v1 room, solve under a timer, and let the original judge decide the result.

Since that post, we kept building, testing, and fixing plenty of details. This is a small update about what has changed.

Hi Codeforces!

I am OmarAfterMidnight, and together with AdhamAfterMidnight we have been working on a project called VoidHub.

During our preparation for the ECPC, AdhamAfterMidnight and I were looking for a way to make practicing more exciting. We wanted something that would push us to solve more problems under real contest pressure while competing directly against each other.

That is when we came up with the idea of building a platform for 1v1 programming battles using problems from Codeforces, Online Judge, and HackerRank.

This experience genuinely brought back my motivation for competitive programming while helping us prepare for the ECPC in a much more enjoyable and competitive way.

Today, I am happy to finally share the result: VoidHub.

Website: https://voidhub.co

What is VoidHub?

VoidHub is a real-time duel platform for competitive programming.

You invite a friend, choose a mode, set the difficulty range, pick a source, and play inside a shared match room with:

• a live timer
• prepared problem statements
• submissions tracking
• penalties
• match results
• profile stats
• ranked and unranked rooms

Codeforces problems are submitted to Codeforces

This is probably the most important part.

If the room uses Codeforces problems, your solution is submitted through your linked Codeforces account. So if you get Accepted, it also appears normally in your Codeforces submissions/profile.

VoidHub is not trying to replace Codeforces. It is more like a duel layer around the original judge.

You still solve real problems, with real verdicts, from the original source.

Match rooms

Inside a room, both players see the same problems and the same timer. The scoreboard updates while the match is running, so you can see who solved what, who is submitting, and how penalties are building up.

Current modes:

• BO3: first to solve 2 problems wins.
• BO5: first to solve 3 problems wins.
• Blitz: short-statement Codeforces problems in a fixed 30-minute race.
• Pick & Play: both players pick topics, and the system builds the problem set around them.

Compiler panel

The room has a compiler/submission panel at the bottom. You choose a language, write or upload your code, and submit from the room.

For Codeforces, the language list is fetched from the linked Codeforces session, so it matches the account setup.

Problem sources

VoidHub currently supports:

• Codeforces
• HackerRank
• Online Judge
• Auto Mix

We also keep metadata such as time limit, memory limit, statement formatting, examples, and source information to prepare rooms faster.

Profiles

Profiles show rating, match count, wins, losses, solved count, recent submissions, friends, and match history.

Dark

Ranked rooms affect rating. Unranked rooms are still recorded in general match stats, but do not affect rating.

Safety notes

A few important points:

• VoidHub does not ask for your Codeforces password.
• Linked judge access is used for things like fetching languages and submitting when you press Submit.
• You can unlink accounts from settings.
• Room results are based on real judge verdicts, not fake local results.
• Privacy settings exist for profile information like email, friends, birth date, and submissions.

Why we are sharing it here

We built VoidHub mainly for people who enjoy practicing with friends.

There are still things we want to improve, and feedback from Codeforces users would be really valuable, especially about:

• match formats
• rating logic
• problem selection
• UI/UX
• fairness rules
• anything that feels annoying during a real duel

You can try it here:

https://voidhub.co

Thanks for reading. Any feedback, bug reports, or ideas are welcome.

I’m not an expert in number theory,

but I was tired of feeling lost.

For a long time, I felt like I was studying in a very random way.

I would learn an idea, solve a few problems, then move on. After a while, I’d forget most of it.

So I decided to try something simple.

Instead of solving randomly, I started grouping problems by topic. Nothing fancy, just trying to build some structure.

For example, I made small sets around:

• Segmented Sieve
• Prime Factorization & Divisors
• Miller-Rabin & Pollard Rho
• Arithmetic on Graphs
• Some basic DP when needed

The goal is not to solve as many problems as possible. The goal is to understand the idea well enough so I don’t feel lost when I see it again.

Right now, I have a set where I solved 22 out of 26 problems, and I’m still stuck on some of them.

But honestly, this way feels much better than random practice.

I’m still learning, and I’m still adding more problems over time.

If you’re also struggling with number theory, maybe the problem isn’t difficulty, maybe it’s just the lack of structure.

I’m putting everything here, and I’ll keep updating it:

https://codeforces.me/group/abU6lmt4Ia/contests

If you have suggestions for good problems or topics I should add, I’d really appreciate it.