Iterator pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the Iterator Pattern Purpose

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

A To enforce strict type checking on elements within a collection.

B To create multiple copies of a collection for parallel processing.

C To provide a way to access elements of a collection sequentially without exposing its underlying representation.

D To convert a collection into a different data structure automatically.

💡 Hint

Think about how you might want to look through items in a box without opening it fully.

The Iterator pattern allows sequential access to elements without revealing the collection's internal structure.

❓ Architecture

intermediate

Components of Iterator Pattern

Which of the following correctly identifies the main components involved in the Iterator pattern?

A Command, Receiver, Invoker, Client

B Observer, Subject, ConcreteObserver, ConcreteSubject

C Factory, Product, ConcreteFactory, ConcreteProduct

D Iterator, Aggregate, ConcreteIterator, ConcreteAggregate

💡 Hint

Focus on the roles that help traverse and hold collections.

The Iterator pattern involves an Iterator interface, an Aggregate interface, and their concrete implementations.

❓ scaling

advanced

Scaling Iterators for Large Collections

When designing an iterator for a very large collection that cannot fit entirely in memory, which approach is most scalable?

A Load the entire collection into memory and iterate over it directly.

B Use a lazy-loading iterator that fetches elements on demand from storage or database.

C Convert the collection into a static array before iteration.

D Duplicate the collection into smaller chunks and iterate each chunk in parallel.

💡 Hint

Think about how to avoid loading everything at once.

Lazy-loading iterators fetch elements as needed, reducing memory usage and improving scalability.

❓ tradeoff

advanced

Tradeoffs in Iterator Design

What is a common tradeoff when implementing an iterator that supports modification of the underlying collection during iteration?

A It increases complexity and may require additional mechanisms to avoid inconsistent states.

B It eliminates the need for an Aggregate interface.

C It simplifies the iterator code but reduces performance drastically.

D It guarantees thread safety without any extra synchronization.

💡 Hint

Consider what happens if the collection changes while you are looking through it.

Allowing modification during iteration requires careful handling to avoid errors or inconsistent data.

❓ component

expert

Iterator Request Flow in a Composite Collection

Consider a composite collection made of multiple sub-collections. Which iterator design best supports seamless iteration over all elements in order?

A A single iterator that internally holds a list of sub-iterators and switches between them as needed.

B Multiple independent iterators running in parallel without coordination.

C An iterator that only iterates the first sub-collection and ignores others.

D A static snapshot of all elements merged into one list before iteration.

💡 Hint

Think about how to move smoothly from one sub-collection to the next.

A composite iterator manages multiple sub-iterators internally to provide a unified traversal.