On playground works well.
Yes it is codewar sandbox problems.
Thanks for the explanation.

Is there someone who also face on with the error?

Done some changes but the code was increased.

There is an error.

STDERR:
error[E0433]: failed to resolve. Use of undeclared type or module `HashSet`
  --> src/lib.rs:18:19
   |
18 |     let mut set = HashSet::new();
   |                   ^^^^^^^ Use of undeclared type or module `HashSet`

error[E0433]: failed to resolve. Use of undeclared type or module `HashSet`
  --> src/lib.rs:18:19
   |
18 |     let mut set = HashSet::new();
   |                   ^^^^^^^ Use of undeclared type or module `HashSet`

error: aborting due to previous error


warning: build failed, waiting for other jobs to finish...
error: aborting due to previous error

error: Could not compile `qualified-rust`.


NOTE: Line numbers in error messages can be incorrect due to concatenation.

Thanks for the answer.

Is it O(n^2) solution?

Can't attend solution with HashMap error in this case https://gist.github.com/mikhail-krainik/9b14c3bd672cfcaea3a0e50504eb8779

Hi everyone. Where I should write about error in compilation for Rust lang? There is error with HashMap when I tried attend the solution.
The error happen only on codewars in other place like official rust playground there no error.