Learn Coding - Off By One

Python, Java, JavaScript Code

Only for iPhone

Free · In-App Purchases · Designed for iPhone. Not verified for macOS.

iPhone

Land the offer: 60+ guided interview lessons in Python, JavaScript, and Java, plus 20 system design stories. Five minutes a day, free to start. Land your next tech job. Off By One turns learning to code and coding interview prep into a five-minute daily habit. Real interview problems, taught the way you actually learn: step by step, with animated visualizations, guided code building, and complexity quizzes. You watch the algorithm move, then you build it yourself, then you prove you understand why it works. No copy-pasting into a judge, no walls of text. WHAT'S INSIDE • 64 guided lessons across 14 topics: arrays and hashing, two pointers, sliding window, stacks, binary search, linked lists, trees, tries, heaps, backtracking, graphs, dynamic programming, greedy algorithms, and intervals • Every lesson in Python, Java, and JavaScript, each written for that language by hand, never transliterated: the JavaScript version asks JavaScript questions, the Java version asks Java questions • Animated, step-by-step visualizations that show how each algorithm actually works: pointers travel, windows slide, trees traverse • Big-O time and space quizzes on every problem, so you can explain the "why" in the room, not just recite the code • 20 system design stories covering caching, load balancing, sharding, CDNs, rate limiting, database indexing, message queues, CAP, WebSockets, and more • A beginner intro for every topic, so you can start from zero and still end up interview-ready • Streaks, weekly progress charts, and an activity grid that keep you honest, five minutes at a time HOW A LESSON WORKS 1. Understand the problem and the approach in plain language 2. Watch the algorithm run, one step at a time 3. Build the solution yourself with guided code steps 4. Answer for its time complexity 5. Answer for its space complexity Finish a lesson and the next one is waiting: the curriculum is ordered so every topic builds on the one before it. WHO IT'S FOR • Complete beginners who want to learn to code with a clear goal • CS students preparing for internship and new-grad interviews • Self-taught developers filling the data structures and algorithms gap • Working engineers brushing up before the next interview loop START FREE Every lesson and story opens free: read the problem, watch the first steps, get a feel for it. Premium unlocks full visualizations, code building, complexity training, and system design. Off By One Premium is an auto-renewing subscription. Plans: annual with a 3-day free trial, monthly with a 3-day free trial, or weekly. Prices are shown in the app in your local currency. Payment is charged to your Apple ID account at purchase confirmation, or when the free trial ends. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the current period. Manage or cancel in your Apple ID settings. Unused trial time is forfeited on purchase. Privacy Policy: https://www.ijustwantagoodjob.com/off-by-one/privacy-policy Terms of Use: https://www.ijustwantagoodjob.com/off-by-one/terms-of-service

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Off By One has a new look and a bigger mission: learn to code, master the interview. • Fresh app icon with full dark mode support • New artwork across the Learn tab • The app now remembers your programming language between lessons • A simpler, cleaner Settings screen • Smaller download, plus polish and fixes throughout Five minutes a day. See you in there.

Version 2.1.0

The developer, I JUST WANT LLC, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Used to Track You

    The following data may be used to track you across apps and websites owned by other companies:

    • Purchases
    • Identifiers
    • Usage Data

  • Data Linked to You

    The following data may be collected and linked to your identity:

    • Purchases
    • Contact Info
    • Identifiers
    • Usage Data

  • Data Not Linked to You

    The following data may be collected but it is not linked to your identity:

    • Diagnostics

Privacy practices may vary based, for example, on the features you use or your age. Learn More

Accessibility

The developer has not yet indicated which accessibility features this app supports. Learn More

Information

Provider
  • I JUST WANT LLC
Size
  • 92.1 MB
Category
  • Education
Compatibility
Requires iOS 15.1 or later.
  • iPhone
    Requires iOS 15.1 or later.
  • iPod touch
    Requires iOS 15.1 or later.
  • Mac
    Requires macOS 12.0 or later and a Mac with Apple M1 chip or later.
  • Apple Vision
    Requires visionOS 1.0 or later.
Languages
English and 6 more
  • English, French, German, Japanese, Korean, Portuguese, Spanish
Age Rating
4+
In-App Purchases
Yes
  • Premium Monthly Subscription USD 3.99
  • Premium Weekly USD 1.99
  • Premium Annually (1 Year) USD 14.99
  • Premium Monthly (1 Month) USD 4.99
  • Premium Annually USD 14.99
  • Premium Weekly USD 1.99
  • Learn More
Copyright
  • © 2026 I JUST WANT LLC
  • Privacy Policy

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