1. Code

class ParkingSystem:
    def __init__(self, big: int, medium: int, small: int):
        self.options = [big, medium, small]

    def addCar(self, carType: int) -> bool:
        # inputs are 1 or 2 or 3
        if self.options[carType-1] > 0:
            self.options[carType-1] -= 1
            return True
        else:
            return False

2. Result

        Runtime : 128 ms(96.48%), Memory usage : 14.8 MB(11.14%)
        (Runtime can be different by a system even if it is a same code.)

Check out the my GitHub repo for more info on the code. If you have questions, you can leave a reply on this post.