# Algorithms & Big O Notation — Data Structures Interview Prep

> Data Structures Interview Prep (iPhone/iPad app by Linh Phan Nhat Khanh.)

- Source: https://appshunter.io/ios/app/algorithms-and-big-o-notation/id6771637608 (this page in markdown: same URL + `.md`)
- Developer: [Linh Phan Nhat Khanh](https://appshunter.io/developer/1777727575)
- Category: Reference, Education
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 17.0 · 4 MB
- Languages: Canadian English, Arabic, Bangla, Catalan, Croatian, Czech, Danish, Dutch, Finnish, French (France) and 34 more
- Released: 2026-05-22
- Data updated: 2026-11-13

## What is Algorithms & Big O Notation?

Look up what an algorithm actually costs, then watch it run. Lichen is a quiet, dark reference and drill app for time and space complexity that works entirely on your device.

THE CATALOG
Thirty classic algorithms across sorting, searching, graphs, trees, strings, dynamic programming, hashing, heaps and greedy methods. Each entry gives you best, average and worst case complexity, space cost, readable pseudocode, a plain-English explanation of how it works, and the situations where you would actually reach for it.

Filter by category or by complexity class, or search by name to jump straight to Quick Sort, Dijkstra, Rabin-Karp or Floyd-Warshall.

STEP THROUGH IT
Sorts, binary search, linear search, BFS and DFS animate frame by frame from instrumented implementations, not canned video. Play, pause, scrub back to the step you missed, slow the speed down, and feel every comparison and swap through haptics. Watching Merge Sort divide and recombine makes n log n stop being an abstraction.

SEE THE CURVES
One growth chart plots O(1), O(log n), O(n), O(n log n), O(n squared), O(2^n) and O(n!) together. Toggle classes on and off and highlight a single line to see just how violently the curves separate as n grows.

DRILL WHAT YOU FORGET
The quiz asks you for the complexity of a given algorithm and scores you. Anything you flag as shaky resurfaces more often, and per-topic accuracy shows where your gaps really are. Your study history is written to the device and nowhere else.

SAVE FOR LATER
Bookmark the algorithms you keep coming back to and keep them in one list.

BUILT FOR
Computer science students facing an exams week, bootcamp graduates, self-taught engineers filling in the theory, and anyone brushing up before a technical loop.

No account, no sign-in, no network calls, no ads. Portrait, dark, and fast enough to check something between train stops.

UNLOCK
Algorithms & Big O Notation requires a Pro unlock to study. Pro opens the complete app: the full catalog of thirty algorithms with best, average and worst case complexity, space cost, pseudocode and plain-English explanations, the step-through visualizer with play, pause, scrub and speed control, the growth chart across every complexity class, the quiz with per-topic accuracy and resurfacing of what you flag as shaky, and bookmarks. Plans: a weekly subscription, a yearly subscription, or a one-time lifetime purchase. Payment is charged to your Apple ID account at confirmation of purchase. The subscription renews automatically unless it is cancelled at least 24 hours before the end of the current period, and your account is charged for renewal within 24 hours prior to the end of the current period. You can manage your subscription and turn off auto-renewal in your Account Settings after purchase.

Privacy policy: https://pnkl26.web.app/privacy-policy
Terms of use: https://pnkl26.web.app/terms-of-service

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Sorting Visualizer | $3.99 | per 7 days |
| Coding Quiz Drills | $19.99 | per year |

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Computer Science Cheat Sheet | $39.99 | one-time |


## Is Algorithms & Big O Notation safe?

Not enough ratings yet to assess Algorithms & Big O Notation.

## Is Algorithms & Big O Notation legit?

Algorithms & Big O Notation appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for Algorithms & Big O Notation is 70 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 2 releases)

### 1.1.0 — 2026-11-12

• Redesigned app with Algorithms, Visualize, Compare and Saved tabs
• Step-by-step visualizer for sorting, search and graph algorithms
• Growth curves, quiz insights, study plan, study history and search
• Lichen Premium added with weekly, yearly and lifetime plans

### 1.0.0 — 2026-05-22

No release notes.

## Apps similar to Algorithms & Big O Notation

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Steel City Time Machine](https://appshunter.io/ios/app/steel-city-time-machine/id6740588943) | 5.0 (3) | Free | Reference |

## More apps by Linh Phan Nhat Khanh

- [AI Voice Notes: Audio to Text](https://appshunter.io/ios/app/ai-voice-notes-audio-to-text/id6737747476)
- [Controller Fly for DJI Drones](https://appshunter.io/ios/app/controller-fly-for-dji-drones/id6752404884)
- [Quick Note: Notepad & Widget](https://appshunter.io/ios/app/quick-note-notepad-and-widget/id6756231129)
- [Year Plan - Goal Planner](https://appshunter.io/ios/app/year-plan-goal-planner/id6760195784)
- [TimeBuddy - World Clock](https://appshunter.io/ios/app/timebuddy-world-clock/id6768292874)
- [Habit Tracker & Mood Journal](https://appshunter.io/ios/app/habit-tracker-and-mood-journal/id6768294604)

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

## Related topics

[computational complexity](https://appshunter.io/ios/topics/computational-complexity) · [algorithmics](https://appshunter.io/ios/topics/algorithmics) · [algorithms quiz](https://appshunter.io/ios/topics/algorithms-quiz) · [complexity](https://appshunter.io/ios/topics/complexity) · [sorting algorithms](https://appshunter.io/ios/topics/sorting-algorithms) · [no algorithm for x](https://appshunter.io/ios/topics/no-algorithm-for-x)

---

*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 2026-11-13.*