Interview Prep

Design Patterns

Reusable solutions to recurring design problems, from the "Gang of Four." Each pattern below has detailed explanations, grouped into Creational, Structural, and Behavioral families.

Creational

Patterns about how objects are created — decoupling construction from use.

Singleton

One shared instance with a global access point.

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Factory Method

Defer instantiation to subclasses via a creation hook.

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Abstract Factory

Create families of related objects without concretes.

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Builder

Assemble complex objects step by step.

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Structural

Patterns about how objects and classes are composed into larger structures.

Adapter

Make an incompatible interface usable by a client.

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Decorator

Add responsibilities dynamically by wrapping.

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Facade

A simple front over a complex subsystem.

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Proxy

A stand-in controlling access to another object.

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Behavioral

Patterns about how objects communicate and distribute responsibility.

Strategy

Swap interchangeable algorithms at runtime.

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Observer

Notify dependents when a subject changes.

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Command

Encapsulate a request as an object.

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Template Method

Fix an algorithm's skeleton, defer steps to subclasses.

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