Refactor Eulerian Path

[sozelfist]

Checklist:

• [x] I ran bellow commands using the latest version of rust nightly.
• [x] I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• [x] I ran cargo fmt just before my last commit.
• [x] I ran cargo test just before my last commit and all tests passed.
• [x] I added my algorithm to the corresponding mod.rs file within its own folder, and in any parent folder(s).
• [x] I added my algorithm to DIRECTORY.md with the correct link.
• [x] I checked COUNTRIBUTING.md and my code follows its guidelines.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.38%. Comparing base (be28ad0) to head (43a332e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #812      +/-   ##
==========================================
+ Coverage   95.36%   95.38%   +0.01%     
==========================================
  Files         311      311              
  Lines       22668    22626      -42     
==========================================
- Hits        21618    21581      -37     
+ Misses       1050     1045       -5     

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[sozelfist]

Can you have a look, @vil02?