[Rishavbhattarai]

TreeSort loses duplicates. BSTRecursiveGeneric ignores a key that is already in the tree (on purpose, and BSTRecursiveGenericTest.testDuplicateInsertions checks it), so sort({-1, -1, 0}) returns [-1, 0, 0]: one -1 is dropped and the array keeps a stale 0 in the last slot. The List overload returns a shorter list.

The fix leaves the BST alone and pairs each element with its input position in a private record, ordered by value and then by position. Equal values stay separate, and the sort is now stable.

TreeSortTest now extends SortingAlgorithmTest, like most other sort tests. On master that brings 6 failures (duplicates, all-identical values, empty strings). With the fix all 44 pass.

• 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. (No new algorithm.)
• All new algorithms include a corresponding test class that validates their functionality. (Regression test added.)
• 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 82.21%. Comparing base (96ed2d7) to head (66ecf25).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7661   +/-   ##
=========================================
  Coverage     82.20%   82.21%           
+ Complexity     8397     8396    -1     
=========================================
  Files           843      843           
  Lines         26133    26134    +1     
  Branches       5097     5097           
=========================================
+ Hits          21482    21485    +3     
+ Misses         3859     3854    -5     
- Partials        792      795    +3     

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[alxkm]

Looks good. Thank you for the contribution.