Added HappyNumber algorithm in maths section

[ruturajjadhav07]

Description

This PR adds an implementation of the Happy Number algorithm in HappyNumber.java along with corresponding unit tests in HappyNumberTest.java.

• Implements cycle detection (Floyd’s Tortoise & Hare method) for efficiency.
• Includes detailed Javadoc and examples.
• Unit tests cover known happy numbers, unhappy numbers, and large input cases.

• 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: Happy Number
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

Notes

• Added both the algorithm and its unit tests.
• Used Wikipedia reference for algorithm definition.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.56%. Comparing base (e788111) to head (12bd616).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6571      +/-   ##
============================================
+ Coverage     76.48%   76.56%   +0.07%     
- Complexity     6010     6014       +4     
============================================
  Files           718      718              
  Lines         20296    20292       -4     
  Branches       3935     3935              
============================================
+ Hits          15524    15536      +12     
+ Misses         4181     4164      -17     
- Partials        591      592       +1     

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[ruturajjadhav07]

Hi
I hope you're doing well! I wanted to follow up on my pull request where I added the HappyNumber algorithm to the maths section of the project. I noticed there hasn’t been any feedback yet, and I just wanted to check if there are any questions or if something is unclear about the changes I made.

Please let me know if you need any further details or adjustments. I’d appreciate any feedback when you get the chance.

Thanks in advance for your time!

[DenizAltunkapan]

@ruturajjadhav07 The interactive Happy Number implementation already exists here: HappyNumbersSeq.java.

However your version is cleaner, better structured, and indeed it belongs in the maths package. Delete the old interactive class in favor of this one. This would improve the library’s organization and maintainability.

[ruturajjadhav07]

@ruturajjadhav07 The interactive Happy Number implementation already exists here: HappyNumbersSeq.java.

However your version is cleaner, better structured, and indeed it belongs in the maths package. Delete the old interactive class in favor of this one. This would improve the library’s organization and maintainability.

I've removed the old HappyNumbersSeq.java file as suggested, keeping the new HappyNumber.java implementation in the maths package. Thanks for the review and feedback!