Updated Stack (#2414)

* * Added type hints
* Added test
* Formated code

* updating DIRECTORY.md

* Update stack.py

* Test error conditions for pop, peek, and

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

Du Yuanchao committed 5y ago

44b8cb0c81b1c86dc8957d6d218f3643488e84a9

Parent: d6bff5c

Committed by GitHub <noreply@github.com> on 9/13/2020, 11:56:03 AM