# 🚀 SDE1 Interview Preparation

A comprehensive repository dedicated to learning, practicing, and mastering **Data Structures & Algorithms (DSA)**, **Object-Oriented Programming (OOP)**,
 **SOLID Principles**, **Design Patterns**, and **Low-Level Design (LLD)** using **Java** and **Kotlin**.

The goal of this repository is to strengthen problem-solving skills, write clean and maintainable code, and prepare for Software Engineer and Android Developer interviews.

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## 🎯 Learning Goals

- Master Data Structures & Algorithms
- Strengthen Object-Oriented Programming concepts
- Learn and apply SOLID Principles
- Implement commonly used Design Patterns
- Practice Low-Level Design through real-world problems
- Improve Java and Kotlin proficiency
- Build interview-ready coding skills

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# 📂 Repository Structure

```text
📦 Java-Kotlin-Interview-Preparation
│
├── Java/
│   ├── Basics/
│   ├── /
│   ├── /
│   └── /
│
├── Kotlin/
│   ├── Basics/
│   ├── /
│   ├── /
│   ├── /
│   └── /
│
├── DSA/
│   ├── Arrays/
│   ├── Strings/
│   ├── HashMap/
│   ├── Stack/
│   ├── Queue/
│   ├── LinkedList/
│   ├── Trees/
│   ├── BinarySearchTree/
│   ├── Heap/
│   ├── Graph/
│   ├── /
│   ├── /
│   └── /
│
├── OOP/
│
├── SOLID/
│
├── DesignPatterns/
│   ├── Creational/
│   ├── Structural/
│   └── Behavioral/
│
├── LowLevelDesign/
│   ├── ParkingLot/
│   ├── ATM/
│   ├── LibraryManagement/
│   ├── BookMyShow/
│   ├── Splitwise/
│   ├── ElevatorSystem/
│   └── FoodDelivery/
│
└── README.md
```

---

# 🛣️ Learning Roadmap

## Data Structures & Algorithms

-[✓] Arrays
-[✓] Strings
-[✓] HashMap
-[✓] HashSet
-[✓] Linked List
-[✓] Stack
-[✓] Queue
- Deque
- Heap / Priority Queue
-[✓] Binary Search
- Trees
- Binary Search Trees
- Graphs
- Recursion
- Backtracking
- Greedy Algorithms
- Dynamic Programming
- Sliding Window
-[✓] Two Pointers
- Prefix Sum
- Bit Manipulation

---

## Object-Oriented Programming

-[✓] Classes & Objects
-[✓] Constructors
-[✓] Encapsulation
-[✓] Inheritance
-[✓] Polymorphism
-[✓] Abstraction
-[✓] Interfaces
-[✓] Abstract Classes
-[✓] Composition
- Aggregation
- Association

---

## SOLID Principles

-[✓] Single Responsibility Principle
- Open/Closed Principle
- Liskov Substitution Principle
- Interface Segregation Principle
- Dependency Inversion Principle

---

## Design Patterns

### Creational

-[✓] Singleton
- Factory
- Builder
- Prototype

### Structural

- Adapter
- Decorator
- Facade
- Composite
- Proxy

### Behavioral

- Observer
- Strategy
- Command
- State
- Template Method
- Iterator

---

## Low-Level Design

Real-world object-oriented design problems including:

- Parking Lot
- ATM
- Library Management System
- Movie Ticket Booking
- Hotel Booking
- Cab Booking
- Food Delivery
- Splitwise
- Elevator System
- BookMyShow

Each implementation focuses on:

- Clean Architecture
- SOLID Principles
- Extensible Design
- Proper Class Relationships
- Maintainable Code

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# ☕ Java Topics

- Core Java
- Collections Framework
- Exception Handling
- File Handling
- Generics
- Multithreading
- Executor Framework
- Streams API
- Functional Interfaces

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# 🟣 Kotlin Topics

-[✓] Kotlin Basics
-[✓] Null Safety
- [✓]Data Classes
- [✓]Sealed Classes
-[✓] Object Declarations
-[✓] Companion Objects
- [✓]Extension Functions
- Higher-Order Functions
-[✓] Scope Functions
- Delegation
-[✓] Coroutines
-[✓] Flow
-[✓] StateFlow
-[✓] SharedFlow

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# 💻 Coding Style

- Clean and readable code
- Proper naming conventions
- Modular structure
- Reusable implementations
- Well-commented where necessary

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# 🎯 Current Goals

- Develop strong problem-solving skills through consistent DSA practice
- Master Java & Kotlin fundamentals
- Implement popular Design Patterns
- Complete 15+ Low-Level Design projects
- Build a strong interview-ready GitHub portfolio
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# 🤝 Contributions

This repository is primarily for learning and interview preparation. Suggestions, improvements, and discussions are always welcome.

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# ⭐ If you find this repository helpful

Please consider giving it a ⭐ to support the project.

Happy Coding! 🚀