DSA Practice System

A dynamic Data Structures and Algorithms practice system that allows you to solve problems and test your solutions in real-time.

🚀 Quick Start

Prerequisites

• Node.js (version 14 or higher)
• npm or yarn

Installation

1. Clone or download the project
2. Navigate to the project directory:

   cd dsa

3. Install dependencies (if any):

   npm install

Running the Application

node runFile.js

📖 How to Use

1. Problem Selection

The system will randomly select problems from the available categories:

• Array Problems (currently active)
• String Problems (commented out)
• Linked List Problems (commented out)

2. Problem Display

For each problem, you'll see:

• Problem Name: Description of what you need to solve
• Input: Sample input data
• Expected Output: What your solution should return
• Input Format: How the input parameters are structured

3. Available Commands

When prompted, you can use these commands:

Command	Action
r or run	Run your current solution against test cases
s or skip	Skip to the next problem
q or quit	Exit the application

4. Solving Problems

Step 1: Understand the Problem

Read the problem description, input format, and expected output carefully.

Step 2: Write Your Solution

Open solution.js in your preferred code editor and modify the solve function:

function solve(arr) {
    // Your solution code here
    // Update the parameters as needed based on the problem
    
    // Example: Reverse an array
    return arr.reverse();
}

Step 3: Test Your Solution

1. Save your changes in solution.js
2. Go back to the running application
3. Type r and press Enter to run the test
4. The system will automatically reload your updated solution

Step 4: Iterate

• If tests fail, you'll see detailed error information
• Modify your solution and test again
• You have 3 attempts per problem before it moves to the next one

🔧 Features

Dynamic Solution Loading

• Real-time Updates: Modify your solution while the program is running
• Automatic Reload: No need to restart the application
• Live Testing: Test changes immediately

Smart Test System

• First Failure Focus: Shows only the first failed test case
• Detailed Error Information: Input, your output, and expected output
• Attempt Limiting: Maximum 3 attempts per problem to prevent getting stuck

Problem Categories

• Array Problems: 7 problems covering various array manipulation techniques
• String Problems: 3 problems for string algorithms
• Linked List Problems: 3 problems for linked list operations

📁 Project Structure

dsa/
├── runFile.js          # Main application file
├── solution.js         # Your solution file (modify this)
├── helperUtils.js      # Utility functions
├── array/              # Array problems
│   ├── index.js        # Array problem collection
│   ├── _01.js          # Problem definitions
│   ├── _01_01.js       # Test cases
│   └── ...             # More problems
├── string/             # String problems
├── linked-lists/       # Linked list problems
└── README.md           # This file

🎯 Problem Types

Array Problems

1. Reverse an Array/String - Basic array reversal
2. Two Number Sum - Find pairs that sum to target
3. Three Number Sum - Find triplets that sum to target
4. Smallest Difference - Find smallest difference between two arrays
5. Monotonic Array - Check if array is monotonic
6. Spiral Traverse - Traverse 2D array in spiral order
7. Longest Peak - Find longest peak in array

String Problems

1. Palindrome Check - Check if string is palindrome
2. Longest Palindromic Substring - Find longest palindrome substring
3. Longest Substring Without Repeating Characters - Find longest unique substring

Linked List Problems

1. Remove Nth Node From End - Remove node from end of list
2. Detect Cycle - Detect cycle in linked list
3. Reverse Linked List - Reverse a linked list

💡 Tips for Success

1. Read Carefully: Understand the input format and expected output
2. Start Simple: Begin with basic approaches, then optimize
3. Test Incrementally: Test your solution after each significant change
4. Use the Error Information: Pay attention to the detailed failure information
5. Don't Get Stuck: Use the skip option if you're struggling with a problem

🔄 Customization

Adding New Problem Categories

1. Create a new folder (e.g., trees/)
2. Add problem files following the naming convention
3. Update runFile.js to include the new category

Modifying Problem Selection

Edit the topic array in runFile.js:

const topic = [
    'array',
    'string',        // Uncomment to include string problems
    'linkedList',    // Uncomment to include linked list problems
]

Changing Attempt Limit

Modify the maxAttempts constant in runFile.js:

const maxAttempts = 5; // Change from 3 to any number

🐛 Troubleshooting

Common Issues

"Error reloading solutions"

• Make sure solution.js has valid JavaScript syntax
• Check that the solve function is properly exported

"Module not found"

• Ensure you're running the command from the correct directory
• Check that all files are present

Tests not updating

• Make sure you save solution.js after making changes
• The system should automatically reload on each test run

📝 Example Workflow

1. Start the application:

   node runFile.js

2. Read the problem:

   Problem => Reverse an Array/String
   Input => [1, 4, 3, 2, 6, 5]
   Expected Output => [5, 6, 2, 3, 4, 1]
   

3. Write your solution in solution.js:

   function solve(arr) {
       return arr.reverse();
   }

4. Test your solution:

• Type r and press Enter
• See the results

5. Iterate and improve until all tests pass!

🎉 Happy Coding!

This system is designed to help you practice DSA problems efficiently. Take your time, understand the problems, and enjoy the learning process!