refactor: improving DisjointSetUnion

[alxkm]

• Added missing path compression in find
• Improved JavaDocs for class and methods
• Cleaned up logic and formatting

• 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 74.60%. Comparing base (7e37d94) to head (3a85699).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6378      +/-   ##
============================================
- Coverage     74.61%   74.60%   -0.02%     
+ Complexity     5454     5453       -1     
============================================
  Files           682      682              
  Lines         19009    19009              
  Branches       3671     3671              
============================================
- Hits          14184    14182       -2     
- Misses         4262     4263       +1     
- Partials        563      564       +1     

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