add: median of medians algorithm in maths

[shubhangiisinghh]

Describe your change:

Added the Median of Medians algorithm implementation.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword.

[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

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[algorithms-keeper]

As there is no test file in this pull request nor any test function or class in the file maths/median_of_medians.py, please provide doctest for the function partition

[algorithms-keeper]

Please provide descriptive name for the parameter: k

[shubhangiisinghh]

The build failure appears to be due to pytest-run-parallel not supporting doctests (thread-unsafe label), which is a known limitation of the test runner rather than an issue with the algorithm itself. All other checks including ruff, pre-commit, build docs, and local doctest runs pass successfully.