that's what I thought !

It is not best practice to have infinite loop. It is better to have same if condition as loop condition and have return statement after while loop.

The two-dimensional int array could be bools instead, making this slightly more readable and lessening the impact of converting from a string (a one-dimensional char array).

читается, просто вы еще не потратили много времени на кодирование

so no guard for num < 0, what happens if num < 0.

Random tests are completely broken:

Test Failed
  Expected: -106
  But was:  1

I second this!!!

exactly , i don't know why people talking about negative values when your code is already pass the goal of the exercise/test

Depends what country you're in.

clever, I had same solution but did n * -1 instead of just -n. Good idea

Clever, but you mutated the list.

Переделывай - это хуйня не читаемая!