Data Structure and Algorithm Practice

A structured collection of algorithm challenges to prepare for 60-minute technical interviews.

📚 Topics Covered

• Arrays & Strings - Manipulation, searching, transformations
• Hash Maps & Sets - Fast lookups, frequency counting
• Two Pointers - Array traversal optimization
• Sliding Window - Subarray/substring problems
• Linked Lists - Traversal, manipulation, cycle detection
• Trees & Binary Search Trees - Traversal, searching, validation
• Graphs - BFS, DFS, connectivity
• Binary Search - Efficient searching in sorted data
• Recursion & Backtracking - Problem decomposition
• Dynamic Programming - Optimization problems (medium level)

📁 Project Structure

interview-prep/
  easy/              # Beginner-friendly challenges
    [challenge-name]/
      problem.md      # Problem description & function skeleton
      solution.js     # Your implementation
      test.js         # Pre-written test cases

  medium/            # Intermediate difficulty challenges
    [challenge-name]/
      problem.md
      solution.js
      test.js

🚀 How to Use

1. Choose a challenge from the easy/ or medium/ directory
2. Read the problem in problem.md
3. Implement your solution in solution.js using the provided skeleton
4. Run the tests to validate your solution:

   node [challenge-name]/test.js

✅ Running Tests

Each challenge includes pre-written test cases. Navigate to the challenge directory and run:

# Example
node easy/two-sum/test.js

Tests use Node.js built-in assert module - no additional dependencies required.

💡 Tips

• Start with easy challenges to build confidence
• Time yourself (aim for 15-20 minutes per easy problem, 25-35 for medium)
• Focus on clarity and correctness first, then optimize
• Practice explaining your approach out loud
• Review multiple solutions after solving

📊 Progress Tracking

• Complete all easy challenges
• Complete all medium challenges
• Revisit and optimize solutions
• Practice whiteboard explanations

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Good luck with your interview preparation! 🎯