Memento pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of the Memento Pattern

What is the primary purpose of the Memento pattern in software design?

A To create a single instance of a class and provide a global point of access to it.

B To capture and externalize an object's internal state so it can be restored later without violating encapsulation.

C To define a family of algorithms, encapsulate each one, and make them interchangeable.

D To separate the construction of a complex object from its representation so the same construction process can create different representations.

💡 Hint

Think about saving and restoring an object's state without exposing its details.

The Memento pattern is used to save and restore the internal state of an object without exposing its implementation details, preserving encapsulation.

❓ Architecture

intermediate

Components of the Memento Pattern

Which of the following correctly identifies the three main components of the Memento pattern?

A Originator, Memento, Caretaker

B Subject, Observer, ConcreteObserver

C Builder, Director, Product

D Component, Decorator, ConcreteDecorator

💡 Hint

Think about who creates the state, who stores it, and who manages it.

The Memento pattern involves the Originator (creates and restores state), the Memento (stores state), and the Caretaker (manages mementos).

❓ scaling

advanced

Scaling Memento Pattern for Large State Objects

When using the Memento pattern for objects with large internal states, what is the best approach to optimize memory usage?

A Use incremental snapshots or delta changes to store only differences between states.

B Avoid using the Memento pattern and instead serialize the entire object to disk after each change.

C Store full copies of the state every time a change occurs to ensure complete rollback capability.

D Keep all mementos in memory indefinitely to allow unlimited undo operations.

💡 Hint

Think about storing only what changes instead of full copies.

Using incremental snapshots or storing only the differences (deltas) between states reduces memory usage and improves scalability.

❓ tradeoff

advanced

Trade-offs of Using the Memento Pattern

What is a common trade-off when implementing the Memento pattern in a system?

A It increases coupling between objects, making the system harder to maintain.

B It violates encapsulation by exposing internal state details to other objects.

C It can lead to high memory consumption due to storing multiple object states.

D It makes the system slower by requiring synchronous communication between components.

💡 Hint

Consider the cost of saving many states over time.

The Memento pattern can consume significant memory because it stores copies of object states, especially if many states are saved.

❓ component

expert

Request Flow in Memento Pattern

In a system using the Memento pattern, what is the correct sequence of interactions when saving and restoring an object's state?

A 3,1,2,4

B 2,1,3,4

C 1,3,2,4

D 1,2,3,4

💡 Hint

Think about who initiates the save and restore actions and the order of storing and restoring.

The Caretaker asks the Originator for a memento, the Originator creates it, the Caretaker stores it, and later the Originator restores state from it.