Longest Substring App

This Django application calculates the length of the longest substring without repeating characters, based on the logic implemented in an algorithm derived from a LeetCode problem. The solution to the problem can also be found in my LeetCode repository.

Features

• Algorithm Integration: The logic for calculating the longest substring without repeating characters is implemented in algorithm.py and integrated into the Django app through the views.py file.
• User Input: A simple HTML form allows users to input a string and calculate the result.
• Database Storage: Results are saved in the database for record-keeping and debugging purposes.

Debugging Process

Initially, the app did not return the correct substring length. Here's the step-by-step debugging process that helped resolve the issue:

1. Algorithm Verification:

   • The logic in algorithm.py was independently verified using unit tests to ensure correctness.

2. Django Debugging:

   • The DEBUG setting in settings.py was set to TRUE:

     DEBUG = True

   • Debugging messages were added in views.py to trace request methods and ensure the correct flow of data:

     print("Received Request: ", request.method)

3. Root Cause Analysis:

   • After testing, the issue was identified in the HTML template. The problem was in the line:

     <p>Longest Substring Length: {{ result.length_of_longest_substring }}</p>

     • The variable name did not match the field in the models.py file.

4. Fix:

   • The incorrect variable name was corrected to:

     <p>Longest Substring Length: {{ result.length_of_longest_substring }}</p>

Files in the Project

• algorithm.py: Contains the logic for calculating the longest substring without repeating characters.
• views.py: Integrates the algorithm with Django views and handles user requests.
• models.py: Defines the SubstringResult model for storing input strings and their corresponding results.
• templates/substring/index.html: The HTML template for the user interface.

How to Run

1. Clone the repository:

   git clone https://github.com/Mike014/LongestSubstringApp.git
   cd LongestSubstringApp

2. Create and activate a virtual environment:

python3 -m venv venv
source venv/bin/activate

3. Install dependencies:

   pip install -r requirements.txt

4. Run migrations:

   python manage.py migrate

5. Start the server:

   python manage.py runserver

Notes

• The algorithm is based on my solution for the LeetCode problem linked above.
• Debugging was essential to ensure the application logic worked seamlessly from the algorithm to the user interface.