* Added minimum waiting time problem solution using greedy algorithm
* [pre-commit.ci] auto fixes from pre-commit.com hooks
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* ruff --fix
* Add type hints
* Added two more doc test
* Removed unnecessary comments
* updated type hints
* Updated the code as per the code review
* Added recursive algo to calculate product sum from an array
* Added recursive algo to calculate product sum from an array
* Update doc string
* Added doctest for product_sum function
* Updated the code and added more doctests
* [pre-commit.ci] auto fixes from pre-commit.com hooks
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* Added more test coverage for product_sum method
* Update product_sum.py
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
