Algorithm: Calculating Product Sum from a Special Array with Nested Structures (#8761)

* 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>