Update DIRECTORY.md with missing files

[Rahul-18r]

• 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 74.15%. Comparing base (ae71861) to head (ea0b1a3).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6301      +/-   ##
============================================
- Coverage     74.16%   74.15%   -0.01%     
+ Complexity     5362     5361       -1     
============================================
  Files           678      678              
  Lines         18686    18686              
  Branches       3625     3625              
============================================
- Hits          13858    13857       -1     
  Misses         4273     4273              
- Partials        555      556       +1     

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