HackerRank Kotlin Android - Swiggy SDE-1 Challenge

📱 Overview

This repository contains my implementation of an Expense Tracker Android application developed as part of Swiggy's Android Machine Coding interview challenge for an SDE-1 role, hosted on HackerRank. The application allows users to track and manage their expenses with features for adding, editing, and viewing expense records.

Note: This repository demonstrates my solution to a code-fixing challenge. Swiggy provided a partially implemented project, and the task was to identify and fix specific issues in the codebase according to requirements.

📸 App Screenshots

📋 Challenge Description

This challenge was part of Swiggy's technical interview process for Android developers, administered through HackerRank's platform.

Task

The challenge required fixing and implementing the Expense list screen in a partially completed Expense Tracker application. The focus was on proper UI implementation, state management, and data handling.

Key Features Implemented

1. A functional list of expense items with proper state handling
2. Add new expense functionality via floating action button
3. Edit existing expense capability
4. Each expense item displays:
   • Description
   • Amount
   • Category
   • Edit button

🛠️ Problems and Solutions

The challenge provided a codebase with several non-functional components. Here's how I approached solving the key issues:

ExpenseListFragment.kt

Problems:

• Incomplete observeData() method missing the LiveData consumption logic
• Missing UI state handling based on ExpenseListStateEvent.UpdateExpenses properties
• Incomplete setupListeners() method for navigating to Add Expense screen

Solutions:

• Implemented proper LiveData observation in observeData() to respond to state changes
• Added conditional UI logic to show/hide expense list based on data availability
• Fixed navigation to Add Expense screen through the AddEditExpenseFragment

ExpensesViewModel.kt

Problems:

• Incomplete updateView() method lacking logic for UI state updates
• Missing implementation for addExpense() to handle adding new expenses
• Missing implementation for editExpense() to update existing expenses

Solutions:

• Implemented updateView() with proper state management:
  • Set showList flag based on list emptiness
  • Provided immutable list copy to ensure adapter triggers proper updates
• Added expense creation logic in addExpense() with LiveData publishing
• Implemented expense editing logic in editExpense() with proper state updates

ExpensesAdapter.kt

Problems:

• Inefficient DiffUtil implementation causing issues with list updates
• Suboptimal item comparison logic

Solutions:

• Optimized DiffUtil implementation for efficient list diffing
• Enhanced item comparison logic to properly detect changes in expense objects
• Improved adapter efficiency for smoother list rendering

🧠 Technical Approach

My approach to solving this challenge:

1. Analysis Phase

   • Thoroughly examined the codebase to identify all incomplete implementations
   • Understood the data flow and architecture of the application
   • Created a roadmap of issues to address in priority order

2. Implementation Strategy

   • Maintained the existing MVVM architecture
   • Used LiveData for reactive UI updates
   • Followed Kotlin best practices
   • Ensured efficient list rendering
   • Handled UI state transitions properly

3. Testing

   • Verified each feature worked as expected
   • Tested edge cases (empty lists, data changes)
   • Ensured smooth UI transitions

💯 Code Quality Focus

Throughout my implementation, I maintained a focus on code quality through:

1. Clean Code Practices

   • Meaningful variable and function names
   • Single Responsibility Principle
   • Proper error handling

2. Kotlin Best Practices

   • Null safety with proper nullable type handling
   • Extension functions where appropriate
   • Idiomatic collection operations

3. Efficient UI Updates

   • Minimizing unnecessary redraws
   • Optimized DiffUtil implementation
   • Proper state management

4. Architecture Adherence

   • Maintaining clear separation of concerns (MVVM)
   • Unidirectional data flow
   • Proper LiveData usage

🚀 Technologies Used

• Kotlin - Primary programming language
• MVVM Architecture - For clean separation of concerns
• LiveData - For reactive UI updates
• RecyclerView & DiffUtil - For efficient list rendering
• Material Design Components - For modern UI elements

🧪 Additional Resources

The repository includes:

1. MCQ Assessment: Multiple-choice questions related to Android development concepts are available in the assets folder. These were part of the theoretical assessment component of the Swiggy interview process.

2. Original Challenge Requirements: The complete problem statement and requirements as provided in the HackerRank challenge.

📝 License

This project is available for educational purposes.

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This repository showcases my solution to Swiggy's Android Machine Coding challenge administered through HackerRank, demonstrating my problem-solving approach and Android development best practices.