[hardikkaurani]

Description

This pull request addresses two issues in LowerBound and UpperBound:

1. Duplicate Elements in LowerBound:
   The Javadoc for LowerBound specifies: "If there are multiple values that are equal to val it returns the index of the first such value."
   Previously, when comp == 0, search() immediately returned median. When an array contained duplicates (e.g., [1, 2, 2, 2, 3]), this returned an intermediate median index instead of the first occurrence. Changing the condition to if (comp <= 0) ensures the search continues exploring the left half to find the first matching element index.
2. Null and Empty Array Safety:
   Added edge case checks in LowerBound.find() and UpperBound.find() to return 0 when array == null, array.length == 0, or key == null, preventing NullPointerException and unexpected behavior on null/empty inputs.
3. Unit Tests:
   Added tests in LowerBoundTest covering duplicate elements, all-identical arrays, empty arrays, null arrays, and null keys, along with null checks in UpperBoundTest.

• 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 algorithms include a corresponding test class that validates their functionality.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

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[hardikkaurani]

Hi @alxkm ! 👋

This PR is ready for review:

1. Duplicate Elements in LowerBound: Per the LowerBound specification ("If there are multiple values that are equal to val it returns the index of the first such value"), updated the condition to search left when comp <= 0 instead of prematurely returning the median element.
2. Null & Empty Array Defensiveness: Safely handles null array, empty array (length == 0), and null key in both LowerBound and UpperBound.
3. Tests & Commits: Structured into 3 atomic commits with comprehensive JUnit test coverage for all-same arrays, duplicate sequences, and null/empty boundary inputs.

Thank you!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.19%. Comparing base (d9b86d1) to head (4d50b7f).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7648      +/-   ##
============================================
+ Coverage     82.17%   82.19%   +0.01%     
- Complexity     8367     8375       +8     
============================================
  Files           842      842              
  Lines         26093    26095       +2     
  Branches       5090     5089       -1     
============================================
+ Hits          21443    21448       +5     
  Misses         3858     3858              
+ Partials        792      789       -3     

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[alxkm]

Thanks! The duplicate fix in LowerBound looks correct, and the tests cover it well.

Three small things:

1. Returning 0 for a null array/key silently hides caller errors. Would Objects.requireNonNull(...) (with assertThrows in tests) be better? If we keep 0, please document it in @return.
2. Without the early return, LowerBound's best case is no longer O(1). Please update the Javadoc.
3. Could you add a duplicates test for UpperBound too (e.g. {1, 2, 2, 2, 3}, key 2 → 4)?

[hardikkaurani]

Hi @alxkm,

Thank you for the review feedback! I have updated the PR to address all three points.

[alxkm]

Looks good. Thank you for the contribution.