C# translation ready! Please review and approve.
Random tests don't seem to be working on c++, unless it is just me
Typescript and Julia translations.
Is it OK that some solutions only work for array sizes up to about 125000? This is because they spread (apply) the array values to function arguments (my solution is in that category also), and stack space is limited.
If you would require solutions to work also with such sizes, then you'd have to add them to the tests.
No random tests (not enough tests) and for example your solution doesn't work for groupDuplicatesAndSort([12, 12, 2, 2, 1, 1]) ;-)