No, it's not. 99 is 'XCIX'.

Is 'IC' a valid Roman numeral for 99 ? I thought so ; and this code wouldn't manage these kind of forms.

'CCD' is not a valid roman numeral:
'CD' is 400
'CCC'is 300

You don't need to validate the form of the Roman numeral.

So 'CCD' won't be passed to the function.

Will give incorrect result for 'CCD' (for example). It will return 200, but should 300.

Will give incorrect result for 'CCD' (for example). It will return 400, but should 300.