Im curious as to why we do not need to specify return "false" or "true" in this example?

Also in Python, Ruby, PHP, maybe all other languages?

doesn't this change the original array?

Thanks for mentioning. I am new on this platform and didn't know the purpose of spoiler flag. Now I knnow. Thanks :)

for int arrays you need to return ints. but you are returning array of chars.

For ruby, I think you should have one test case where the duplicate values are not consecutive. for example:

unique_in_order([1, 2, 3, 2, 2, 4])

Result should be:

unique_in_order([1, 2, 3, 2, 4])

Use spoiler flag, please.

You get this error when you pass a negative value to Math.sqrt. You can't pass negative to it.