Here are the precise instructions you can paste into the README.md file for your GitHub Classroom assignment:

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Longest Substring with K Unique Characters

Problem Statement

Write a Python function that finds the longest substring of a given string that contains exactly K unique characters. If no such substring exists, return 0.

Function Signature:

def longest_substring_k_unique(s: str, k: int) -> int:

Example Input/Output:

1. Example 1:

   Input: S = "araaci", K = 2
   Output: 4
   Explanation: The longest substring with exactly 2 unique characters is "araa".
   

2. Example 2:

   Input: S = "cbbebi", K = 3
   Output: 5
   Explanation: The longest substring with exactly 3 unique characters is "cbbeb" or "bbebi".
   

3. Example 3:

   Input: S = "aa", K = 1
   Output: 2
   Explanation: The longest substring with exactly 1 unique character is "aa".
   

Constraints:

1. The string S will have at least one character and at most 10^6 characters.
2. The integer K will be between 1 and the number of distinct characters in the string.

Instructions

1. Fork the Assignment Repository:

   • Click on the "Fork" button in the top right corner of this repository to fork it into your own GitHub account.

2. Clone Your Forked Repository:

   • Clone the repository to your local machine using the following command in your terminal:

     git clone https://github.com/<your-github-username>/source-code-management-exercise.git

   • Replace <your-github-username> with your GitHub username.

3. Create a New Branch:

   • In your local repository, create a new branch to work on your solution:

     git checkout -b gcd-feature

4. Implement Your Solution:

   • Implement the longest_substring_k_unique function in the provided solution.py file. Ensure your code handles edge cases and test it thoroughly before submission.

5. Commit Your Changes:

   • Once you’ve written and tested your solution, stage and commit the changes:

     git add solution.py
     git commit -m "Implemented solution for longest substring with K unique characters"

6. Push the Changes:

   • Push your changes to the gcd-feature branch on your forked repository:

     git push origin gcd-feature

7. Create a Pull Request:

   • Go to your forked repository on GitHub.
   • Click the "Compare & pull request" button to create a pull request back to the original repository.
   • Make sure you are comparing your gcd-feature branch with the main branch of the original repository.
   • Submit the pull request.

Peer Review

Once you submit your pull request, you will be assigned a peer’s solution to review. Follow these steps for peer review:

1. Review the Peer’s Code:

   • Check the peer’s code for correctness, efficiency, and readability.
   • Provide constructive feedback and suggest improvements where necessary.

2. Submit Your Feedback:

   • Use the GitHub review feature to submit your feedback.

Submission Deadline

Please make sure your pull request is submitted before the deadline: [INSERT DEADLINE DATE].

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Notes:

• Ensure your code follows the required Python function signature.
• Make sure your solution is efficient and can handle large inputs (up to 10^6 characters).
• Be respectful and constructive in your peer reviews.