Design Patterns Quick Overview

Design patterns are reusable solutions to common software design problems. Here's a very-short breakdown of the three main categories:

Creational Patterns

• Singleton: One instance, global access.
• Factory Method: Interface-driven object creation.
• Abstract Factory: Create related objects without specifying concrete classes.
• Builder: Step-by-step complex object construction.
• Prototype: Clone existing objects.

Structural Patterns

• Adapter: Bridge between incompatible interfaces.
• Decorator: Dynamically add behavior to objects.
• Facade: Simplify complex systems with a unified interface.
• Composite: Tree structures for part-whole hierarchies.
• Proxy: Placeholder to control access.
• Bridge: Separate abstraction from implementation.
• Flyweight: Share common data to save memory.

Behavioral Patterns

• Observer: Notify changes to dependent objects.
• Strategy: Swap algorithms dynamically.
• Command: Encapsulate requests as objects.
• State: Change behavior based on state.
• Template Method: Algorithm structure with flexible steps.
• Mediator: Simplify object communication.
• Chain of Responsibility: Pass requests along a handler chain.
• Iterator: Sequentially access collection elements.
• Visitor: Add operations without altering object structure.

Knowing when and how to apply these patterns is key to acing your system design interview. Prepare to discuss real-world use cases!