* Tighten up psf/black and flake8
* Fix some tests
* Fix some E741
* Fix some E741
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
* Add sol3 for project_euler proble_03
* Update sol3.py
add type hint
remove unused variable
* Format code with psf/black
* add sol3 to project_euler/problem_08, modify the stepsize of the loop,will be faster than sol1