The Must-Solve 150.
Every question is a real implementation, debugging or architecture task. Work through the levels in order, or jump straight to what your next interview needs.
10 of 150 questions
Hard
50 questions, 45–90 minutes each
Senior-level correctness, architecture and production constraints.
Advanced machine coding & DSA
Spreadsheets, editors, IDEs and the data structures behind them.
- 141Build a fully accessible component library including modal, dropdown, combobox, and keyboard interactions
- 142Build an Excel-like spreadsheet with editing, formulas, dependency tracking, and virtualized rendering
- 143Build a collaborative rich-text editor with remote cursors and offline synchronization
- 144Implement a browser IDE with syntax highlighting, files, tabs, and isolated code execution
- 145Build a Trello-like Kanban app supporting nested cards, drag-and-drop, undo/redo, and persistence
- 146Implement an autocomplete search engine using a TrieFree
- 147Implement a dependency resolver using topological sorting
- 148Implement a median tracker for a real-time data stream
- 149Build a graph-based workflow editor with cycle detection and execution ordering
- 150Build an interactive coding playground with sandboxing, test execution, worker-based timeouts, and persisted solutions