[dpittaluga76]

Describe your change

Adds searches/radix_binary_search.py, implementing Radix Binary Search for sorted integer sequences.

The implementation builds a prefix directory and performs binary search within the selected bucket. It returns the first matching index, or None when the target is absent. It supports negative integers, duplicates, and empty inputs.

Includes explanatory comments, a worked example, input validation, 17 passing doctests, and a reference to the SOSD paper. The implementation was reviewed and tested.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Doctests accompany the new algorithm; no existing algorithm or tests are modified.
• Documentation change? -- Comments and docstrings within the new file.

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. To ease review, please open separate PRs for separate algorithms.
• 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 locally. GitHub CI results are pending.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.