CodeSequence

CodeSequence teaches data structures and algorithms along a clear path: first you understand the idea, then you watch it work step by step, recall it without looking and, finally, apply it to real problems.

A PATH IN THE RIGHT ORDER - 12 chapters and 35 topics ordered by dependency, from complexity analysis and arrays to graphs and dynamic programming. - Every lesson in four steps: Understand, Visualize, Retrieve and Connect. - The app always shows you your next lesson.

WATCH IT WORK - Interactive animations for arrays, linked lists, stacks, queues, trees, heaps, graphs and sorting algorithms. - Move step by step, adjust the speed and follow every pointer, index and decision. - Diagrams, Big-O complexity tables and common mistakes for every topic.

REMEMBER IT FOR REAL - Quick questions in every lesson, with an explanation for each answer. - Code exercises: fill in snippets and match concepts. - Spaced-review cards that come back right as you start to forget them, with optional reminders.

PRACTICE WITHOUT SPOILERS - 102 interview problems, with a broad set of easy problems to get started. - Progressive hints that unlock in order, and solutions you only see after you've tried. - Reasoned solutions, from brute force to optimal, in Swift, Python, Java and JavaScript. - An editor to write your solution and run it. - Interview mode: a random problem against a 45-minute clock.

A PLAN FOR EVERY DAY - The Today screen suggests three short steps: learn, review and apply. - Streak, recent activity and mastery by topic, just for you.

BUILT FOR STUDYING - In English and Spanish; switch language whenever you like. - Light and dark mode, and text that adapts to the size you use on your iPhone or iPad. - For iPhone and iPad.

Your progress stays on your device. No accounts, no ads and no leaderboards. Your code is only sent to an execution service when you tap Run.

Discovery signals