Enum usage (VehicleType, SpotType) in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Enum Role in Parking Lot Design

In a parking lot system, VehicleType and SpotType enums are used. What is the main purpose of using enums here?

A To restrict vehicle and spot categories to predefined constant values for clarity and safety.

B To allow dynamic creation of vehicle and spot types at runtime.

C To store vehicle and spot data in a database table.

D To randomly assign vehicle types to spots.

💡 Hint

Think about how enums help avoid errors by limiting options.

Enums define fixed sets of constants, ensuring only valid vehicle and spot types are used, improving code safety and readability.

❓ Architecture

intermediate

Mapping VehicleType to SpotType in Design

Which design best represents the relationship between VehicleType and SpotType enums in a parking lot system?

A Each VehicleType maps to one or more compatible SpotTypes to check parking eligibility.

B SpotType values are randomly assigned to VehicleType values without mapping.

C VehicleType and SpotType enums are merged into a single enum for simplicity.

D VehicleType enum contains SpotType values as its members.

💡 Hint

Consider how the system knows which vehicle fits which spot.

Mapping VehicleType to compatible SpotTypes allows the system to validate if a vehicle can park in a given spot type.

❓ scaling

advanced

Scaling Enum Usage for New Vehicle and Spot Types

When adding new vehicle and spot types frequently, what is the best approach to keep the enum usage scalable and maintainable?

A Create a separate enum for each new vehicle and spot type pair.

B Hardcode all new types directly into enums and recompile the system each time.

C Remove enums and use plain strings everywhere for flexibility.

D Use enums with extension mechanisms or configuration files to add new types without code changes.

💡 Hint

Think about how to avoid frequent code changes for new types.

Using extension points or configs allows enums to be flexible while preserving type safety and maintainability.

❓ tradeoff

advanced

Tradeoffs Between Enum and Database Lookup for SpotType

What is a key tradeoff when choosing between using enums or a database table to represent SpotType in a parking system?

A Enums are slower to access than database queries.

B Database tables cannot represent SpotType relationships.

C Enums offer compile-time safety but less flexibility; database allows dynamic updates but adds latency.

D Enums require a database connection to function.

💡 Hint

Consider flexibility versus performance and safety.

Enums provide fixed, fast, and safe values at compile time; databases allow dynamic changes but with overhead and potential errors.

❓ estimation

expert

Estimating Capacity for Enum-Based Parking Spot Allocation

A parking system uses enums for VehicleType and SpotType. Given 3 VehicleTypes and 4 SpotTypes, with each VehicleType compatible with 2 SpotTypes, estimate the minimum number of spot instances needed to support 100 vehicles simultaneously, assuming uniform distribution and no sharing.

A At least 150 spots, assuming some spot types can serve multiple vehicle types.

B Exactly 100 spots, one per vehicle regardless of type.

C At least 200 spots, because each vehicle needs a unique compatible spot.

D At least 300 spots, to cover all combinations of vehicle and spot types.

💡 Hint

Think about how many spots are needed if each vehicle must have a compatible spot without sharing.

To support 100 vehicles simultaneously with no sharing, the minimum number of spot instances required is 100—one per vehicle. Enums ensure compatibility between vehicles and spots but do not increase the total number of spots needed beyond the vehicle count.