Add/generate parentheses iterative approach (#10024)

* Generate parantheses iterative

* Generate parantheses iterative

* Generating parantheses code using iterative approach

* Update generate_parentheses_iterative.py

* updating DIRECTORY.md

* Update generate_parentheses_iterative.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update generate_parentheses_iterative.py

* Update generate_parentheses_iterative.py

* Update generate_parentheses_iterative.py

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Co-authored-by: nightmare10123 <[email protected]>
Co-authored-by: Maxim Smolskiy <[email protected]>
Co-authored-by: MaximSmolskiy <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>