# Lichen: Big-O Algorithms — Algorithm complexity reference

> Algorithm complexity reference (iPhone/iPad app by Linh Phan Nhat Khanh.)

- Source: https://appshunter.io/ios/app/lichen-big-o-algorithms/id6771637608 (this page in markdown: same URL + `.md`)
- Developer: [Linh Phan Nhat Khanh](https://appshunter.io/developer/1777727575)
- Category: Reference, Education
- Price: Free
- Age rating: 4+
- Requires: iOS 17.0 · 1 MB
- Languages: American English
- Released: 2026-05-22
- Data updated: 2026-06-11
- User reviews in markdown: https://appshunter.io/ios/app/lichen-big-o-algorithms/id6771637608/reviews.md

## What is Lichen?

Lichen is a focused, offline reference for classical algorithms and their Big-O complexity. Built for students, interview candidates, and working engineers who want fast answers without noise.

A clean catalog, a side-by-side growth chart, and a quick quiz mode — all on a single dark stage. No clutter, no popups, no upsells.

KEY FEATURES
• Catalog of 30+ algorithms across Sort, Search, Graph, Tree, String, Dynamic Programming, Divide & Conquer, Greedy, Hashing, and Heap
• Best, average, worst, and space complexities for every algorithm
• Live growth-rate chart comparing O(1), O(log n), O(n), O(n log n), O(n²), O(2ⁿ), and O(n!)
• Pseudocode snippets and real-world use cases on every detail page
• Filter by category and by complexity class with single-tap chips
• Bookmark algorithms you want to revisit
• Big-O Quiz mode for spaced practice before interviews

DESIGNED FOR INTERVIEW PREP
Whether you are warming up for a coding round, picking the right data structure for a hot loop, or refreshing concepts before a system design call, Lichen stays out of the way and surfaces the answer in two taps.

PRIVACY
No tracking. No accounts. Your bookmarks live on your device.


## Version history (last 1 release)

### 1.0.0 — 2026-05-22

No release notes.

## More apps by Linh Phan Nhat Khanh

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All apps by Linh Phan Nhat Khanh: https://appshunter.io/developer/1777727575

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-11.*