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Design a Parking Lot

Starting an object-oriented design interview for a parking lot scenario involves several key steps to ensure a structured and thorough approach. Here's a suggested outline:

  1. Clarify Requirements:

    • Begin by asking clarifying questions to fully understand the requirements and constraints of the parking lot system. This may include:
      • The size and capacity of the parking lot.
      • Types of vehicles allowed (e.g., cars, motorcycles, trucks).
      • Parking rules and regulations (e.g., reserved spaces, handicapped spots).
      • Payment methods and pricing models.
      • Operational considerations (e.g., entry/exit points, security measures).
      • Any additional features or functionalities required.

  2. Identify Objects and Responsibilities:

    • Based on the requirements gathered, identify the main objects and their responsibilities within the parking lot system. This may include:
      • ParkingLot: Representing the parking lot itself.
      • Vehicle: Representing different types of vehicles.
      • ParkingSpace: Representing individual parking spaces.
      • Ticket: Representing parking tickets issued to vehicles.
      • Entrance/Exit: Representing entry and exit points.
      • PaymentSystem: Handling payment processing.
      • SecuritySystem: Managing security measures (e.g., surveillance).
    • Define the attributes and behaviors (methods) of each object.

  3. Define Relationships:

    • Establish relationships between the identified objects. For example:
      • ParkingLot has ParkingSpaces and Entrance/Exit points.
      • Vehicle occupies ParkingSpace(s) and obtains Ticket(s).
      • PaymentSystem interacts with Ticket(s) to process payments.
      • SecuritySystem monitors ParkingLot and Entrance/Exit points.
    • Determine the multiplicity and cardinality of relationships (e.g., one-to-one, one-to-many).

  4. Design Class Diagram:

    • Create a class diagram to visually represent the relationships between objects. Use UML notation to depict classes, attributes, methods, and associations.
    • Ensure that the class diagram accurately reflects the identified objects and their interactions.

  5. Consider Design Patterns:

    • Evaluate whether any design patterns (e.g., Factory, Singleton, Strategy) are applicable to optimize the design and address specific requirements.
    • Integrate relevant design patterns into the class diagram as needed.

  6. Discuss Trade-offs and Scalability:

    • Discuss any trade-offs involved in the design decisions made, such as performance vs. simplicity, flexibility vs. efficiency, etc.
    • Consider how the design can accommodate future scalability and extensibility requirements.

  7. Validate and Iterate:

    • Validate the design with the interviewer, ensuring that it aligns with the requirements and addresses all key aspects of the parking lot system.
    • Be prepared to iterate on the design based on feedback and further discussions with the interviewer.

By following this structured approach, you can effectively tackle an object-oriented design interview question for designing a parking lot system, demonstrating your ability to analyze requirements, identify objects, define relationships, and create a well-structured design.

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