Method new

1603-design-parking-system.rs:7–12

(big: i32, medium: i32, small: i32)

impl ParkingSystem {
    fn new(big: i32, medium: i32, small: i32) -> Self {
        ParkingSystem {
            max: vec!(big, medium, small),
            current: vec![0; 3]
        }
    }

    fn add_car(&mut self, car_type: i32) -> bool {
        let car_type = car_type as usize - 1;