As a world's leading online programming learning platform, LeetCode is quite popular among programmers. Since each problem has a unique number id, users tend to share problems via id. However, it is not convenient to visit problem page directly via id. People have to visit LeetCode Problems firstly, then enter that number id in the 'Search questions' input box, press 'enter', click the problem title link, finally comes to the problem page. What a hard work!
This simple project, called LCid, provides directly access to LeetCode problems via id. Features:
- Fetch all LeetCode problems via crawler.
- Redirect to LeetCode problem page with problem id in the URL path via backend.
- Support both LeetCode global site and China site redirect.
- CI/CD, fetch all LeetCode problems daily and commit back to the repository via GitHub Actions, then deploy the latest snapshot.
LCid is now available at lcid.cc. Just add /<problem-id> at the end of lcid.cc (e.g. lcid.cc/1), then browser will redirect you to the problem page. Simple, fast, and make your live easier.
What's more, to redirect to China site, add /cn/<problem-id> instead (e.g. lcid.cc/cn/1). Interested in the brief info of the problem? Try /info/<problem-id> (e.g. lcid.cc/info/1) and find more!
Use Python 3.11 for the crawler and local backend, matching the GitHub Actions workflow.
The crawler is implemented with urllib3 and backend is powered with flask.
To install all those dependencies, execute pip install -r requirements.txt.
The frontend is built with React.js with Ant Design UI.
To build frontend, use Node.js 22.x with npm 10.x.
(older versions may work but not tested)
Updated Oct 29 2023, leetcode.com now protected with Cloudflare. To send request to any page or endpoint under leetcode.com, cf_clearance and csrftoken are required.
For now, it is difficult to automate way to get both cf_clearance and csrftoken. Therefore, it is okay to manually get from browser for now.
Once we fetched cf_clearance and csrftoken from browser, copy file .env to .env.local, fill both fields accordingly.
VITE_BACKEND_API_URL="http://localhost:1437"
LC_CF_CLEARANCE="{manually get from browser}"
LC_CSRFTOKEN="{manually get from browser}"
To fetch all problems, execute python fetch_problems_all.py. The crawler fetches problems in pages, reports progress, and saves the results to problems_all.json in JSON format.
To start frontend, install all dependencies via npm install first. Then, start frontend development server via npm run start. By default, the development server will starts at http://localhost:3000.
To build frontend, use npm run build. The built frontend will be created at build/.
To start backend service, execute python app.py <port> (e.g. python app.py 1437). Then, the backend server will start at localhost:<port>.
Now you can try the following endpoints. All of them should work correctly.
localhost:<port>/localhost:<port>/1localhost:<port>/cn/1localhost:<port>/info/1
To deploy on Vercel, use the checked-in vercel.json. The build command npm run build creates the frontend in build/ and copies problems_all.json to build/info.json. The configuration serves /info from that static snapshot and routes /info/<id>, /cn/<id>, and /<id> to api/problem.js.
Keep VITE_BACKEND_API_URL empty when building for production so the frontend fetches /info from the same origin.
The daily GitHub Actions workflow updates problems_all.json on main when the fetched data changes. To enable it, configure LC_CF_CLEARANCE and LC_CSRFTOKEN as repository secrets. Deploy the updated snapshot to refresh /info.
POSTHOG_PROJECT_TOKEN enables optional redirect usage statistics through PostHog in Vercel production deployments. Leave it unset to disable analytics.
- This is just a naive tool for convenient access and only call LeetCode API at low frequency. It only obtains public accessible data (no personal info or paid content collected and distributed). DO NOT ABUSE LEETCODE API!!!
- GitHub Repo: bunnyxt/lcid
- Author: bunnyxt
- License: MIT