Changelog
New features, content, and improvements to returnzero.
Ten new multi-level coding challenges - Basic Calculator, LRU Cache, Merge Intervals Family, Lowest Common Ancestor Family, Binary Tree Vertical Order, Valid Palindrome With Deletions, Weighted Random Pick, Nested List Weights, Kth Largest Element, and Dasher Payout Engine.
Seventeen new LeetCode-style practice questions across the DSA core concepts - arrays, binary search, bit manipulation, DFS, dynamic programming, graphs, greedy, hash maps, queues, recursion, sorting, trees, and union find - each with labeled examples, constraints, and a Solution Breakdown.
Every DSA core concept page now follows one structure - standalone canonical example pages, LeetCode-style problem formatting with labeled examples and constraints, a renamed Solution Breakdown section, and difficulty-ordered question sets.
Sign in and practice with AI on any free problem - guided practice, the coding assistant, and interview mode now work on the free tier with generous session and token limits. DSA mock interviews stay premium.
Every study domain now has a course landing page with curriculum, progress, and live algorithm animations. The algorithm visualizer learned four new algorithms - merge k-sorted lists (heap and pairwise), minimum window substring, and robot room cleaner - plus a 2D grid view.
Book and join collaborative peer interview practice rooms with real-time canvas sharing and scheduling.
All DSA surfaces now support Python, JavaScript, and TypeScript side by side - code blocks, practice questions, and the live editor.
A guided coach leads you through system-design problems step by step on a scaffolded canvas, with a debrief at the end. Available from any mobile system-design article or the problems catalog.
PremiumA redesigned dashboard with a Kanban-style prep board to track problems you're working on, an activity heatmap to keep your streak visible, and shared SWE plans - all in a cleaner layout.
A new Anthropic interview-process guide and a deep article on AI safety considerations for interview settings.
Five new practical coding challenges: Thread-Safe KV Store, Web Crawler, Image Processing Pipeline, Image Pipeline 2, and Persistent KV Store.
Interview-process guides for 12 companies, with references. Guides are updated regularly as we get new reports from candidates - check back for new additions.
18 deep articles covering data structures and algorithms fundamentals, 85 linked practice questions, and detailed animated visualizations for every concept - heaps, graphs, trees, sliding window, and more.
Practice coding interviews with an AI interviewer in a live IDE, and review your past sessions on a dedicated My Sessions dashboard.
PremiumFlashcard-style review cards with spaced repetition to reinforce system-design and core concept knowledge over time.
PremiumA structured Coding Interview Intro covering what coding interviews look like, what they test, and where to start - with guides on challenge shapes, the four-phase protocol, and code review rounds.
New core concept primers for Android system design - build systems (Gradle/Bazel), app size and delivery, and testing strategies.
15 new interview-prep coding questions covering arrays, hash maps, sliding window, trees, stacks, and more - linked to their core concept articles.