Refactor KMP and RabinKarp: Improve Reusability and Test Coverage

[divyanshsaxena002]

Description

This PR refactors the KMP and RabinKarp algorithms to improve their design, reusability, and testability.

Changes

• Refactoring:
  • Removed main methods and console System.out.println statements.
  • Updated methods to programmatically return a List<Integer> of match indices instead of printing them.
  • Removed dependency on java.util.Scanner in RabinKarp.
• Bug Fixes:
  • Fixed an integer overflow issue in RabinKarp by implementing modular exponentiation for hash calculation.
  • Fixed a StringIndexOutOfBoundsException when the pattern length exceeds the text length.
  • Implemented safer rolling hash updates to handle negative modulo cases correctly.
• Testing:
  • Added comprehensive JUnit tests (KMPTest.java and RabinKarpTest.java).
  • Added explicit tests for edge cases: null inputs, empty strings, and hash collisions.
  • Ensured high code coverage to meet build requirements.

Checklists

• Test passed locally
• Code formatted correctly

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.37%. Comparing base (11eec78) to head (01f597a).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7250      +/-   ##
============================================
+ Coverage     79.10%   79.37%   +0.26%     
- Complexity     6983     7014      +31     
============================================
  Files           784      784              
  Lines         22971    22970       -1     
  Branches       4515     4519       +4     
============================================
+ Hits          18171    18232      +61     
+ Misses         4077     4017      -60     
+ Partials        723      721       -2     

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