Refactor Anagram

[sozelfist]

Checklist:

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

[sozelfist]

Can you have a look, @vil02?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.40%. Comparing base (858443e) to head (bd326fc).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #825   +/-   ##
=======================================
  Coverage   95.40%   95.40%           
=======================================
  Files         313      313           
  Lines       22699    22708    +9     
=======================================
+ Hits        21655    21664    +9     
  Misses       1044     1044           

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