Would've been cool if it was stated that the tree is expected to be sorted. Would solve all confusion around the .insert() and remove() methods.

my first ever 1 kyu i will be back ))

Oh... thank you. il'try...

you misunderstood the task. look at the error messages, the sample tests and the description: you are supposed to return a function that can be called. Your current implementation returns a char. this is why the tests complain that called object type 'char' is not a function

you are not supposed to write your own main() function on Codewars. If you do, the tests cannot work correctly, as they provide their own. Also, please use markdown formatting when posting code.

approved by someone

fixed, thanks for your report

I think the description example code is wrong for Java. You cannot call a Supplier with parenthesis like supplier(). In Java you have to call the get() method on it like so: supplier.get().

The example in the description should call the supplier in this way: abc.get();

OCaml translation (author gone)

Haskell translation

approved

looks like it was rejected