Update infix to postfix (#3817)

* add test to infix_to_postfix_conversion

* fixed pre-commit error

* fixed build error

* updating DIRECTORY.md

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

Du Yuanchao committed 5y ago

786b32431cd1d0f57ec4b79a009959da8a2fe06c

Parent: d8f573c

Committed by GitHub <noreply@github.com> on 11/1/2020, 4:35:31 PM