Scaffold, test, and submit LeetCode problems in Java — with an Anki-inspired rating step that drives a hardest-first practice queue.
[!WARNING]
Under active development. LeetKnight is pre-1.0. Commands, data-file schemas (.leetknight/reviews.json, per-problem .leetknight.json), and the rating workflow may change between versions without a migration path. Feedback and issue reports are welcome.
What it does
LeetKnight is a VS Code extension for interview prep on LeetCode in Java. It:
Scaffolds problems locally — pick from the LeetCode catalog (or paste a URL) and it creates <slug>/Solution.java with the official Java starter (plus a Time/Space complexity header) alongside <slug>/notes.md with the problem description.
Runs & submits from the editor — ▶ runs your solution against LeetCode's own example test cases via the "Run Code" endpoint; ☁️ submits it for real. Both use LeetCode's java runtime — nothing is compiled locally.
Grades your recall — after every Accepted submission, a modal asks you to rate the attempt (Hard / Medium / Easy). Ratings drive the practice panel, grouped 🔴 Hard → 🟡 Medium → 🟢 Easy so the ones you found hardest sit at the top. Within a group the oldest attempts come first so you don't see the same problem every session.
Re-solves on demand — click any problem in the panel and it opens Solution.java and resets it back to the starter (no confirmation prompt) so you can re-solve it from scratch. The random-pick button picks one at random (interview-mode: no idea what's coming).
Install
Requirements
Python 3.10+ on your PATH (python3 --version must work). The bundled helper scripts use it to talk to LeetCode's API.
pip install requests beautifulsoup4 — used by the bundled scripts.
VS Code 1.85+.
No local JDK required. LeetCode compiles and runs your submission on their servers.
Then in a new folder run LeetKnight: Initialize Workspace from the Command Palette to seed .leetknight/reviews.json.
LeetCode setup
Test/Submit hit LeetCode's authenticated endpoints, so LeetKnight needs your browser session cookies:
Log in to leetcode.com in your browser.
Open DevTools → Application → Cookies → https://leetcode.com.
Copy the values of LEETCODE_SESSION and csrftoken.
Run LeetKnight: Set LeetCode Cookies from the Command Palette and paste them (they're stored in VS Code's SecretStorage, backed by your OS keychain).
Cookies typically last ~2 weeks. When they expire you'll see an [auth] message telling you which one to refresh.
Daily workflow
Add a problem — LeetKnight: Search LeetCode (or New Problem from URL). Picks land at <workspace>/<slug>/ and the Solution.java auto-opens.
Iterate — click ▶ to run example cases. Fast, doesn't count as a submission, uses LeetCode's own judge.
Submit — click ☁️, confirm y in the terminal. On Accepted, a modal pops up: How hard was this? Pick Hard / Medium / Easy (dismissing defaults to Easy).
Practice later — open the LeetKnight activity-bar entry. Your solved problems are grouped by rating with hardest at the top. Click any row to re-solve — it opens the file and resets to the starter in one step. Or click the random-pick button for interview mode.
Reset manually — the ↻ button in the editor toolbar resets Solution.java back to the starter. Panel-click and random-pick do the same as part of opening the problem, so you don't need to reset separately.
Commands
Command
What it does
LeetKnight: Initialize Workspace
Create .leetknight/reviews.json in the current folder
LeetKnight: Search LeetCode
Fuzzy-search the catalog and scaffold the pick
LeetKnight: New Problem from URL
Scaffold a specific LeetCode URL
LeetKnight: Run Tests (▶)
Run example cases via interpret_solution
LeetKnight: Submit (☁️)
Real submission; opens Hard/Medium/Easy modal on Accepted
LeetKnight: Reset Problem (↻)
Reset Solution.java to the starter
LeetKnight: Pick Random Practice Problem
Open a random tracked problem for re-solving
LeetKnight: Set LeetCode Cookies
Paste LEETCODE_SESSION + csrftoken
How it works
Every problem you scaffold gets a hidden <slug>/.leetknight.json cache containing the LeetCode questionId, exampleTestcases, and the original initialCode. This means Run / Submit / Reset don't need to re-hit LeetCode's rate-limited GraphQL endpoint on every invocation.
Ratings and attempt history live in a single <workspace>/.leetknight/reviews.json — human-readable, git-committable, portable between machines. This is populated organically as you submit; there is no bulk history import.
Communication between the Submit script and the VS Code extension happens via <workspace>/.leetknight/pending.json: the Python script writes it on Accepted, the extension tails it with a FileSystemWatcher, pops the rating modal, and deletes the file.
Language is fixed to Java. Every problem is scaffolded from LeetCode's java code snippet, and Run/Submit send "lang": "java" to the judge.
