Big-O Complexity Analyzer & Code Playground

Instant Big-O time & space analysis for coding problems on leetcode.com, plus a built-in code playground. Free; AI is optional.

Know the Big-O of your solution in seconds — then write, run and analyze code in a built-in IDE. Free, private and offline-first. Big-O Complexity Analyzer & Code Playground helps you understand and improve your code while you practice coding problems. It analyzes the time and space complexity of your solution, explains the approach you used and suggests a better one — on leetcode.com problem pages and in a full Playground inside the extension. HIGHLIGHTS • Instant Big-O analysis — time and space complexity with a clear verdict (Excellent / Efficient / Room to improve / Needs optimization), the approach you used, and a suggested alternative. Works offline, with no sign-up. • Optional AI — an honest status: the settings show "AI is working" only after a real test request succeeded, and say exactly what is wrong otherwise (rejected key, retired model, quota, overload). Add your own API key. Get a complete optimized solution, a step-by-step dry run, edge cases and tips. Each provider keeps its own key; choose the model, the explanation style and the solution language. • Code Playground (a small IDE) — write or paste code in a real code editor: syntax highlighting for 10 languages, line numbers, auto-indent, bracket matching, code folding, autocomplete and search. Work with several files like in VS Code: create, rename and delete files, open files from your computer, and import one file from another. Smart suggestions like VS Code (snippets, methods after a dot, names from all your files, imports between files) and VS Code shortcuts (F5 run, Ctrl+Enter new line, Alt+Up/Down move line, Ctrl+/ comment, Ctrl+D). Drag the divider to resize the editor and output. Run Python, JavaScript and TypeScript right in your browser and see output, logs, errors and input — the page scrolls to the result for you. Analyze code in any language with one click. • A road map to DSA mastery — 71 patterns in the order to learn them, drawn as a winding road with a marker that shows where you are, how many patterns and hours are left, a title that grows as you do, and a celebration with confetti and sounds each time you complete a pattern, a stage or the whole road. Each pattern has three LeetCode problems; connect LeetCode (optional) and the road map checks that you really solved them. Free; nothing leaves your browser. • DSA patterns course — 71 patterns that cover almost every interview problem (two pointers, sliding window, binary search, heaps, greedy, tries, graphs, topological sort, Dijkstra, dynamic programming, union-find and more). Each lesson explains the idea in plain words, how to spot it and the steps, with code in JavaScript, Python and Java, a dry run, the time and space cost, practice problems and common mistakes — plus an animated simulation you can play, step through, slow down or speed up, and run on an input size you choose. No other course needed. • Practice toolkit — beside the analysis in the Playground and on a page of its own, with every feature explained: run your code against test cases (input and expected output, pass or fail, with the first differing line), check a complexity against the problem's limits ("will it pass at n = 10^5?"), draw arrays, grids, linked lists, binary trees and graphs, drop in classic algorithm templates (binary search, BFS, DFS, union-find, Dijkstra, trie, DP, heap and more in Python, JavaScript, Java and C++), and use everyday developer tools (JSON formatter, regex tester, Base64/URL, timestamps, hashes, UUIDs). • Developer tools — one searchable page of 21 utilities with input and result side by side: JSON formatter and validator, JWT decoder, regex tester, text diff, Base64 and URL encoding, JSON to CSV and TypeScript types, URL parser, HTML entities and escaping, cron explainer with the next run times, number bases and bit grid, colour converter with contrast checker, password, lorem and UUID / ULID generators, chmod calculator, an HTTP status reference, an ASCII and Unicode table and an API explorer for free public APIs (or your own). Colour-coded results, adjustable text size, and everything runs in your browser; the only thing that leaves it is a request you send yourself from the API explorer. • Make it yours — 26 color themes including all of VS Code's built-in ones (Dark Modern, Dark+, Light+, Monokai, Solarized, Abyss, High Contrast and more) plus Dracula, One Dark, GitHub, Tokyo Night, Nord and others, 18 fonts, text size, line height, ligatures, tab size, spaces or tabs, word wrap, line numbers, whitespace, and output side by side or below — all behind a single settings icon. A sun / moon button switches the settings site between light and dark without touching the popup on LeetCode. • Track your progress — history with problem numbers and links, a daily streak, an activity heatmap, a weekly efficiency trend that shows whether your solutions are getting faster, and breakdowns by complexity and language. Export to CSV. • Big-O cheat sheet — growth chart, constraints-to-complexity guide, data structures, sorting algorithms and problem-solving patterns, all searchable. • On the problem page — analyze from the floating button or with Alt+Shift+A. When you click the site's own Analyze button, the extension can show its analysis in the same place. • Learning mode — a spoiler guard keeps the full solution hidden until you choose to reveal it. PRIVATE BY DESIGN • No third-party analytics, no ads. An account is optional: the extension works fully without one, and then nothing is collected. • Python and JavaScript run locally in your browser; your code is not uploaded in order to run it. Files you create or open stay in the page's memory and are never stored or uploaded. • Your code is sent for AI analysis only when you ask for it. With your own key it goes straight from your browser to the one provider you selected. Without a key, signed-in users can allow the free shared AI: the code goes to our server and on to the AI provider, to be analysed, and is not stored or logged. "Offline only" blocks all network use. • Keys, settings and history stay in your browser. History never contains your code. • Optional account — create one to back up your settings, progress and history so they come back after reinstalling or on another computer. Your API keys are never uploaded, and your code is not uploaded to the account (it is sent to our server only for a single analysis you ask for with the free shared AI, and is not stored); you can download or delete everything from the Account page. HOW TO USE 1. Open any problem on leetcode.com and click "Analyze complexity", or press Alt+Shift+A. 2. Click the extension icon to open the settings. Try the Playground: click "Load example", then Run and Analyze. Use the + in the tab bar to add a file and import it from your main file. 3. Optional: choose an AI provider and paste your key to unlock the full solution, dry run and edge cases. Great for coding interview preparation, data structures and algorithms (DSA) practice, and for understanding why a solution is O(n log n) rather than O(n²). GOOD TO KNOW • The built-in analyzer is a structural estimate. AI results are better but can still be wrong — always check against the problem's constraints. • AI providers may charge for usage under your own account with them. The free shared AI has a daily limit per user and can be switched off by the owner at any time; with your own key there is no such limit. • Compiled languages (Java, C++, Go and others) can be analyzed but not run in the browser. Not affiliated with, endorsed by, or sponsored by LeetCode or any AI provider. All product names and trademarks belong to their respective owners.