I started with the entities and drew out ParkingLot, Level, ParkingSpot, and the Vehicle hierarchy pretty quickly.
Start by clarifying requirements and constraints (e.g., vehicle types, spot sizes, levels, entry/exit points, payment). Then identify core entities and their relationships, sketch a class diagram with clear responsibilities, and implement key classes focusing on encapsulation and extensibility. Finally, discuss trade-offs and potential extensions.
Pro tip: Emphasize extensibility by using interfaces and design patterns (e.g., Strategy for pricing, Factory for spot creation) and discuss how to handle concurrency for spot allocation. This shows you think beyond basic OOP and consider real-world scalability.
Ask questions to understand scope: vehicle types (car, motorcycle, truck), spot sizes (compact, large, handicapped), levels, entry/exit, payment, and any constraints. Confirm assumptions.
List main classes: ParkingLot, Level, ParkingSpot, Vehicle (with subclasses), Ticket, Payment, and possibly EntryPanel/ExitPanel. Define relationships (e.g., ParkingLot has Levels, Level has Spots).
Sketch classes with fields and methods, ensuring single responsibility. Use inheritance for vehicles and spots, and interfaces for behaviors like pricing or spot allocation.
Code key classes (e.g., ParkingLot, Level, ParkingSpot, Vehicle) with proper encapsulation (private fields, getters/setters) and extensibility (abstract classes/interfaces).
Talk about design choices (e.g., inheritance vs composition), concurrency handling, and how to extend for new vehicle types or pricing strategies.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Multi-spot assignment for trucks is where things got messy.
Start by clarifying requirements: vehicle sizes, spot sizes, and whether spots are contiguous. Then design data structures to track spot occupancy and efficiently find contiguous free spots for multi-spot vehicles, ensuring O(1) or O(log n) operations for park and leave. Finally, discuss availability_summary aggregation and trade-offs between simplicity and scalability.
Pro tip: Mention that you would use a segment tree or interval tree to quickly find contiguous free spots, but also consider a simpler approach like a linked list of free blocks if the parking lot is small. This shows you balance efficiency with practical constraints.
Ask about vehicle sizes (e.g., motorcycle, car, bus), spot sizes, whether spots must be contiguous, and expected scale. Confirm if availability_summary should report counts by spot size or vehicle type.
Propose a data structure to represent spots (e.g., array or linked list) and track occupancy. For multi-spot vehicles, consider a segment tree or interval tree to find contiguous free blocks efficiently.
Describe the algorithm: find a contiguous block of free spots matching the vehicle's size, mark them occupied, and store the assignment (e.g., vehicle ID to spot indices). Handle failure if no block exists.
Look up the vehicle's assigned spots, mark them free, and update any data structures (e.g., merge adjacent free blocks). Ensure the vehicle is removed from tracking.
Aggregate free spots by size or contiguity. If using a segment tree, you can query the number of free spots or largest contiguous block. Discuss time complexity and potential optimizations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Start by outlining your core design for a parking lot system, emphasizing modularity and extensibility. Then, for each future requirement, explain how you would extend the design without major refactoring, using principles like separation of concerns and design patterns. Conclude by discussing trade-offs and how you would validate the design against these evolving needs.
Pro tip: Demonstrate foresight by anticipating not just the listed features but also potential interactions between them, such as how multi-tenant lots might affect billing and reservations. This shows you think holistically about system evolution.
Briefly describe the initial design for a parking lot system, focusing on key entities like ParkingLot, Spot, Vehicle, and Ticket, and how they interact.
Highlight areas in the design that are likely to change, such as pricing, spot allocation, and lot management, and explain how you've made them extensible.
For each requirement (hourly billing, reservations, EV-charging, multi-tenant), explain the necessary additions or modifications, referencing design patterns like Strategy, Observer, or Decorator.
Analyze the trade-offs of your approach, such as increased complexity versus flexibility, and how the design scales with more features or tenants.
Summarize how the design accommodates future needs and mention how you would test or validate the extensibility, perhaps through unit tests or prototyping.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.