refactor: TwoPointers

[alxkm]

Class cleanup.
Readability improvements.
Added tests.

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.90%. Comparing base (b231a72) to head (620f4aa).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5380   +/-   ##
=========================================
  Coverage     46.90%   46.90%           
  Complexity     2903     2903           
=========================================
  Files           525      525           
  Lines         15363    15364    +1     
  Branches       2908     2908           
=========================================
+ Hits           7206     7207    +1     
  Misses         7855     7855           
  Partials        302      302           

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