⚡ CP Arena

A competitive programming judge for VS Code. Compile, run, and test your solutions against multiple test cases without leaving your editor.

✨ Features

Feature	Description
🧪 Test Case Management	Add, edit, delete, and re-run test cases from the sidebar
▶️ One-Click Run	Compile once and run every test case, or re-run just one
📡 Competitive Companion	Auto-import problems and test cases from Codeforces, AtCoder, CodeChef, and other judges
✅ Instant Verdicts	`AC` / `WA` / `TLE` / `RTE` / `CE` with per-case execution time
🎯 Forgiving Output Check	Token-based comparison ignores extra whitespace; `YES`/`NO` matched case-insensitively
⏱ Relaxed Time Limit	Runs are judged against 2.5× the problem's stated limit, so slower local hardware doesn't cause false `TLE`s
🛡 Runaway Guard	A 16 MB output cap kills solutions stuck printing in an infinite loop
🛑 Stop Anytime	Kill a running solution instantly, including child processes
📤 Quick Submit	Copies your code and opens the judge's submit page
🔁 CPH Compatible	Problems created by Competitive Programming Helper (`.cph`) are imported automatically
🚦 ONLINE_JUDGE Toggle	Compile C/C++ with `-DONLINE_JUDGE` straight from the sidebar

🚀 Getting Started

Install

Open Extensions in VS Code, search for CP Arena, and click Install.

Requirements

VS Code 1.80.0 or later
A compiler or interpreter for the language you use, available on your PATH
(Optional) The Competitive Companion browser extension for importing problems

Important: CP Arena does not bundle any compiler. Before your first run, set the compile/run command for your language to match what's installed on your machine. See Set up your compiler.

🔧 Set up your compiler

CP Arena ships with generic defaults, but compiler names and flags vary between machines and operating systems. Edit the command for your language to match your own setup before running anything.

Open Settings → Extensions → CP Arena, or add the setting directly to your settings.json.

C++

The default is g++ -O2 -std=c++17. Change it to whatever your system provides:

{
  // Standard g++ (most Linux distros, MinGW / MSYS2 on Windows)
  "cp-arena.cpp.compileCommand": "g++ -O2 -std=c++17",

  // Homebrew GCC on macOS (version-suffixed binary)
  "cp-arena.cpp.compileCommand": "g++-15 -O2 -std=c++23",

  // Clang
  "cp-arena.cpp.compileCommand": "clang++ -O2 -std=c++17",

  // Codeforces-like build with extra warnings and a larger stack
  "cp-arena.cpp.compileCommand": "g++ -O2 -std=c++20 -Wall -Wextra"
}

Anything valid on your command line works here — add sanitizers, change the standard, point at an absolute compiler path, whatever you need. CP Arena appends the source file and output path automatically, so don't include them yourself.

Other languages

{
  "cp-arena.c.compileCommand": "gcc -std=c17 -O2 -Wall",
  "cp-arena.rust.compileCommand": "rustc -O",
  "cp-arena.java.compileCommand": "javac",
  "cp-arena.java.runCommand": "java",
  "cp-arena.python.runCommand": "python3"   // use "python" on most Windows setups
}

Verifying your compiler

If a run fails with a "command not found" style error, the command isn't on your PATH. Check it in a terminal first:

g++ --version
python3 --version

Whatever name works there is the name to put in your settings.

📖 Usage

Import a problem

Install Competitive Companion, open a problem page, and click the extension's + icon. CP Arena creates the source file, saves the sample tests, and opens everything in the sidebar.

Open a problem locally

Open any supported source file (.cpp, .c, .py, .java, .rs, .go) and the sidebar attaches to it. If no saved problem exists, you get an empty workspace where you can add your own test cases.

Run

Click ▶ Run All in the sidebar, or use the Run Tests button in the status bar. Your file is saved and compiled first, then each case runs in turn. Cards collapse on AC and expand on failure, so only the problems need your attention.

To re-run a single case, click the ▶ on that card.

Submit

Click the Submit icon. CP Arena saves the file, copies your code to the clipboard, and opens the matching Codeforces submit page (contest, gym, group, and problemset URLs are all handled). Paste and submit.

If the problem has no saved URL, you'll be prompted for one.

`ONLINE_JUDGE` toggle

The OJ switch in the bottom bar controls whether -DONLINE_JUDGE is passed to the C/C++ compiler, so you can keep local debug output behind an #ifndef ONLINE_JUDGE guard without editing code between runs.

⚙️ Settings

Setting	Default	Description
`cp-arena.general.defaultLanguage`	`cpp`	Language used for newly imported problems
`cp-arena.general.timeLimit`	`3000`	Time limit recorded on locally created problems (ms)
`cp-arena.general.companionPort`	`10043`	Port the Competitive Companion listener binds to
`cp-arena.general.savePath`	(workspace root)	Where imported problem files are written
`cp-arena.cpp.compileCommand`	`g++ -O2 -std=c++17`	C++ compile command
`cp-arena.c.compileCommand`	`gcc -std=c17 -O2 -Wall`	C compile command
`cp-arena.java.compileCommand`	`javac`	Java compile command
`cp-arena.java.runCommand`	`java`	Java run command
`cp-arena.rust.compileCommand`	`rustc -O`	Rust compile command
`cp-arena.python.runCommand`	`python3`	Python interpreter

The sidebar shows the problem's original time limit, but runs are enforced against 2.5× that limit. Local hardware, cold binary starts and editor overhead rarely match the original grading server, so enforcing the exact limit tends to produce false TLEs.

🛠 Supported Languages

Language	Mode	Default tool
C++	compiled	`g++`
C	compiled	`gcc`
Rust	compiled	`rustc`
Java	compiled, then run	`javac` + `java`
Python	interpreted	`python3`
JavaScript	interpreted	`node`
Go	compiled and run	`go run`

📋 Commands

Available from the command palette (Ctrl+Shift+P / Cmd+Shift+P):

Command	Description
`CP Arena: Run All Test Cases`	Compile and run every test case
`CP Arena: Add Test Case`	Append an empty test case
`CP Arena: Stop Execution`	Kill the running solution
`CP Arena: Clear All Test Cases`	Remove all test cases from the current problem
`CP Arena: Submit Code`	Copy code and open the submit page

🧠 How Verdicts Work

AC — output matches
WA — tokens differ. Trailing whitespace and newlines are ignored, and YES/NO compare case-insensitively
TLE — exceeded 2.5× the problem's time limit, or produced more than 16 MB of output
RTE — non-zero exit code or a fatal signal such as SIGSEGV
CE — compilation failed; the compiler's output is shown in the sidebar

🏗 Building from Source

git clone https://github.com/AashwatJain/cp-arena.git
cd cp-arena
npm install
npm run build        # bundles src/ into dist/ with esbuild
npx vsce package     # produces a .vsix

Press F5 in the project to launch a VS Code window with the extension loaded for debugging.

📜 License

See LICENSE.md.

Made for competitive programmers

CP Arena

Aashwat Jain