这份 notebook 由 Donne Martin 准备。Source 和 license info 在 GitHub。

设计 Parking Lot

Constraints & assumptions

需要支持哪些 vehicle types？
- Motorcycle, Car, Bus
不同 vehicle type 占用的 parking spots 数量是否不同？
- Yes
- Motorcycle spot -> Motorcycle
- Compact spot -> Motorcycle, Car
- Large spot -> Motorcycle, Car
- Bus 需要 5 个连续的 large spots
Parking lot 是否有 multiple levels？
- Yes

Solution

%%writefile parking_lot.py
from abc import ABCMeta, abstractmethod


class VehicleSize(Enum):

    MOTORCYCLE = 0
    COMPACT = 1
    LARGE = 2


class Vehicle(metaclass=ABCMeta):

    def __init__(self, vehicle_size, license_plate, spot_size):
        self.vehicle_size = vehicle_size
        self.license_plate = license_plate
        self.spot_size = spot_size
        self.spots_taken = []

    def clear_spots(self):
        for spot in self.spots_taken:
            spot.remove_vehicle(self)
        self.spots_taken = []

    def take_spot(self, spot):
        self.spots_taken.append(spot)

    @abstractmethod
    def can_fit_in_spot(self, spot):
        pass


class Motorcycle(Vehicle):

    def __init__(self, license_plate):
        super(Motorcycle, self).__init__(VehicleSize.MOTORCYCLE, license_plate, spot_size=1)

    def can_fit_in_spot(self, spot):
        return True


class Car(Vehicle):

    def __init__(self, license_plate):
        super(Car, self).__init__(VehicleSize.COMPACT, license_plate, spot_size=1)

    def can_fit_in_spot(self, spot):
        return True if (spot.size == LARGE or spot.size == COMPACT) else False


class Bus(Vehicle):

    def __init__(self, license_plate):
        super(Bus, self).__init__(VehicleSize.LARGE, license_plate, spot_size=5)

    def can_fit_in_spot(self, spot):
        return True if spot.size == LARGE else False


class ParkingLot(object):

    def __init__(self, num_levels):
        self.num_levels = num_levels
        self.levels = []

    def park_vehicle(self, vehicle):
        for level in levels:
            if level.park_vehicle(vehicle):
                return True
        return False


class Level(object):

    SPOTS_PER_ROW = 10

    def __init__(self, floor, total_spots):
        self.floor = floor
        self.num_spots = total_spots
        self.available_spots = 0
        self.parking_spots = []

    def spot_freed(self):
        self.available_spots += 1

    def park_vehicle(self, vehicle):
        spot = self._find_available_spot(vehicle)
        if spot is None:
            return None
        else:
            spot.park_vehicle(vehicle)
            return spot

    def _find_available_spot(self, vehicle):
        """Find an available spot where vehicle can fit, or return None"""
        # ...

    def _park_starting_at_spot(self, spot, vehicle):
        """Occupy starting at spot.spot_number to vehicle.spot_size."""
        # ...


class ParkingSpot(object):

    def __init__(self, level, row, spot_number, spot_size, vehicle_size):
        self.level = level
        self.row = row
        self.spot_number = spot_number
        self.spot_size = spot_size
        self.vehicle_size = vehicle_size
        self.vehicle = None

    def is_available(self):
        return True if self.vehicle is None else False

    def can_fit_vehicle(self, vehicle):
        if self.vehicle is not None:
            return False
        return vehicle.can_fit_in_spot(self)

    def park_vehicle(self, vehicle):  # ...
    def remove_vehicle(self):  # ...

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