A free, open-source flashcard app for coding interview preparation. Drill all 209 problems from the LeetCode 75 and Top Interview 150 study plans as flashcards or as a grid guessing game — each card carries a hint, an approach, time/space complexity, and a concise Python solution.
Runs entirely in your browser. No backend, no sign-up, no tracking, no runtime network
calls — your progress and notes live in localStorage, with optional backup to a JSON
file or sync through a secret GitHub gist you own.
▶ Try it live · Features · Problem coverage · Run locally · FAQ
Grinding problems teaches you to solve that problem. Interviews reward recognising the pattern fast — seeing "Array / String" and reaching for two pointers, or recognising a sliding window before you write a line. This app drills recall and pattern recognition rather than typing: you see a title, you commit to a problem type and a Big-O guess, and only then do you get the answer.
- Browse mode — a minimized card cover (title only). On the back: reveal the answer, reveal the problem type, and guess time/space complexity from a dropdown.
- Grid game — a 4×4 board where a tile only flips when you correctly guess its type, time, and space complexity. Clear the board and load more rows.
- Switch between All, LeetCode 75, Top Interview 150, or your own collections, built in the Sets ⚙ panel.
- Filter by category, difficulty (Easy / Medium / Hard), or status; shuffle (
s); full keyboard navigation. - Mark cards Got it (
1) or Review again (2) — progress persists locally.
A persistent scratch space attached to each problem for drafting solutions and parking ideas. One note per card, reachable from the card back, the grid tile, and the ⓘ modal, saved as you type.
Add custom cards via a form or batch-import JSON, and export them back out. See the JSON format below.
Export or import your entire state as JSON, or keep it in a secret GitHub gist so
notes and progress follow you between machines. It needs only a personal access token
with the gist scope — no backend, no account system, no third party. Syncs merge per
card by edit time, so two devices can both write and neither loses work.
All 209 problems (75 from LeetCode 75 + the 134 Top Interview 150 problems not already in it), preloaded with statement, hint, approach, complexity, and Python solution:
| Pattern | Cards | Pattern | Cards |
|---|---|---|---|
| Array / String | 31 | Backtracking | 8 |
| Binary Tree — DFS | 17 | Two Pointers | 7 |
| Linked List | 15 | Heap / Priority Queue | 7 |
| Hash Map / Set | 13 | Math | 6 |
| DP — Multidimensional | 12 | Binary Search Tree | 6 |
| Binary Search | 10 | Matrix | 5 |
| Graphs — DFS | 9 | Intervals | 5 |
| Stack | 8 | Graphs — BFS | 5 |
| Sliding Window | 8 | Binary Tree — BFS | 5 |
| DP — 1D | 8 | Trie | 4 |
| Bit Manipulation | 8 | Divide & Conquer | 4 |
Plus Queue, Prefix Sum, Monotonic Stack, and Kadane's algorithm.
git clone https://github.com/kaziridwan/leetcode-flashcards.git
cd leetcode-flashcards
npm install
npm run dev # dev server
npm run build # production build → dist/
npm run preview # preview the built bundleRequires Node 18+. The stack is Vite 5 + React 18 with no router, no state library, and no CSS framework.
The app is a static Vite build (output dist/) and deploys to either platform with no
code changes. Use a button above, or set it up manually:
- Button: click Deploy to Vercel above — it clones the repo and auto-detects
Vite (build
npm run build, outputdist). Novercel.jsonneeded. - Manual: Vercel → Add New… → Project → import the repo → Deploy.
- CLI:
npm i -g vercel && vercel --prod
- Button: click Deploy to Cloudflare above — it clones the repo and reads
wrangler.toml(pages_build_output_dir = "dist"). - Manual: Cloudflare → Workers & Pages → Create → Pages → connect the repo →
framework preset Vite, build command
npm run build, output directorydist. - CLI:
npm i -g wrangler && npm run build && wrangler pages deploy dist
public/_redirects(/* /index.html 200) ships an SPA fallback for Cloudflare so any path resolves to the app. Vercel ignores it harmlessly.
Replace kaziridwan/leetcode-flashcards in the button links above if you fork the repo
to a different path.
A JSON array (or single object). Only title is required:
[
{
"title": "Two Sum",
"difficulty": "Easy",
"category": "Hash Map / Set",
"link": "https://leetcode.com/problems/two-sum/",
"hint": "Store complements in a hash map.",
"approach": "One pass: for each x, check if target - x was seen.",
"complexity": "Time O(n) · Space O(n)",
"code": "def twoSum(nums, target): ..."
}
]See sample-import.json for a working example.
Is it free? Yes — MIT-licensed and free to self-host. There is nothing to pay for and no account to create.
Does my data leave my browser? No, unless you explicitly connect a GitHub gist in the Sync panel. Nothing fetches on load; there is no analytics and no telemetry.
Does it use spaced repetition? Not yet. Cards use a two-bucket Got it / Review again model. An SM-2 / Leitner scheduler is on the roadmap.
Is this an Anki deck? No — it's a standalone web app, so there's nothing to install and the complexity-guessing drills and grid game have no Anki equivalent.
What language are the solutions in? Python. A per-card language toggle is on the roadmap.
Can I add my own problems? Yes — via the add form or a JSON import, and you can group them into your own problem sets.
Can I use it on my phone? Yes, the layout is responsive.
Project documentation lives in docs/wiki/ —
Architecture, Data Model,
Features, and the Decision log.
Issues and pull requests are welcome. If you (or an agent) change the code, follow the
wiki-update protocol in CLAUDE.md to keep the docs current. New to the
repo? Start with
agent-context/claude-code-handoff.md.
LeetCode flashcards · DSA flashcards · data structures and algorithms practice · coding interview preparation · LeetCode 75 · Top Interview 150 · Blind 75 alternative · Big-O complexity quiz · algorithm pattern recognition · technical interview study tool
MIT — see LICENSE.