Strategy pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the core benefit of the Strategy pattern

Which of the following best describes the main advantage of using the Strategy pattern in system design?

A It allows changing the algorithm's behavior at runtime without modifying the client code.

B It enforces a single fixed algorithm implementation throughout the system.

C It tightly couples the algorithm implementation with the client, improving performance.

D It eliminates the need for interfaces or abstract classes in the design.

💡 Hint

Think about flexibility and how behavior can be swapped easily.

The Strategy pattern enables selecting an algorithm's behavior at runtime by encapsulating algorithms in separate classes. This allows the client to switch strategies without changing its own code.

❓ Architecture

intermediate

Identifying components in a Strategy pattern architecture

In a typical Strategy pattern design, which component is responsible for selecting and using a specific strategy implementation?

A The Client code directly

B The Context class

C The Concrete Strategy classes

D The Strategy interface

💡 Hint

Consider which part holds a reference to the strategy and delegates work.

The Context class maintains a reference to a Strategy object and delegates the execution to it. It controls which strategy is used.

❓ scaling

advanced

Scaling Strategy pattern for multiple algorithms

You have a system using the Strategy pattern with 3 algorithms. The system needs to support 20 algorithms without changing the Context class. What is the best approach to scale this design?

A Implement each new algorithm as a new Concrete Strategy class and register them dynamically with the Context.

B Add all new algorithms as methods inside the Context class and use conditional statements to select them.

C Modify the Strategy interface to include all 20 algorithms as default methods.

D Create a single Concrete Strategy class that handles all algorithms internally with if-else logic.

💡 Hint

Think about how to keep the Context class unchanged and maintain open/closed principle.

Adding new algorithms as separate Concrete Strategy classes and registering them dynamically allows scaling without modifying the Context, adhering to open/closed principle.

❓ tradeoff

advanced

Tradeoffs when using the Strategy pattern

What is a common tradeoff when applying the Strategy pattern in a system design?

A Tight coupling between the Context and Concrete Strategies.

B Inability to add new algorithms without modifying existing code.

C Reduced flexibility in changing algorithms at runtime.

D Increased number of classes and objects, which can complicate the system structure.

💡 Hint

Consider the impact on codebase size and complexity.

The Strategy pattern increases the number of classes because each algorithm is a separate class, which can make the system more complex to manage.

❓ component

expert

Request flow in a Strategy pattern implementation

Consider a payment processing system using the Strategy pattern to support multiple payment methods (credit card, PayPal, crypto). Which sequence best describes the request flow when processing a payment?

A Client processes payment → Strategy selects Context → Context executes algorithm → Strategy returns result

B Strategy selects Context → Client processes payment → Context calls Strategy → Strategy executes algorithm

C Client selects payment method → Context sets corresponding Strategy → Context calls Strategy to process payment → Strategy executes algorithm

D Context processes payment → Client selects Strategy → Strategy executes algorithm → Context returns result

💡 Hint

Think about who chooses the strategy and who executes it.

The client chooses the payment method, the Context sets the appropriate Strategy, then delegates the payment processing to that Strategy.