Added randomized algorithms

[Mishu03]

Add Two Randomized Algorithms

This PR adds two new randomized algorithms to the repository:

1. Reservoir Sampling – Randomly selects k items from a stream of unknown length.
2. Randomized QuickSort – Sorts a list using QuickSort with a randomly chosen pivot for better average-case performance.

All implementations follow Python 3.13+ standards, include type hints, docstrings, and doctests, and return results instead of printing. The code is fully compliant with repository guidelines and ready for automated testing via GitHub Actions.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my feature works
• New and existing unit tests pass locally with my changes

[algorithms-keeper]

Click here to look at the relevant links ⬇️

🔗 Relevant Links

Repository:

• Contributing guidelines
• Project Euler solution guidelines

Python:

• Formatted string literals (f-strings)
• Type hints
• doctest
• unittest
• pytest

Automated review generated by algorithms-keeper. If there's any problem regarding this review, please open an issue about it.

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[algorithms-keeper]

Please provide descriptive name for the parameter: n

Please provide descriptive name for the parameter: k

[algorithms-keeper]

Please provide descriptive name for the parameter: k