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.