{"id":"ood-parking-lot","title":"Design a parking lot","sections":[{"id":"constraints-and-assumptions","title":"Constraints and assumptions","html":"Constraints and assumptions
\n\n- What types of vehicles should we support?\n\n
\n- Does each vehicle type take up a different amount of parking spots?\n
\n- Yes
\n- Motorcycle spot -> Motorcycle
\n- Compact spot -> Motorcycle, Car
\n- Large spot -> Motorcycle, Car
\n- Bus can park if we have 5 consecutive \"large\" spots
\n
\n \n- Does the parking lot have multiple levels?\n\n
\n
","headings":[]},{"id":"solution","title":"Solution","html":"Solution
\nfrom abc import ABCMeta, abstractmethod\n\n\nclass VehicleSize(Enum):\n\n MOTORCYCLE = 0\n COMPACT = 1\n LARGE = 2\n\n\nclass Vehicle(metaclass=ABCMeta):\n\n def __init__(self, vehicle_size, license_plate, spot_size):\n self.vehicle_size = vehicle_size\n self.license_plate = license_plate\n self.spot_size = spot_size\n self.spots_taken = []\n\n def clear_spots(self):\n for spot in self.spots_taken:\n spot.remove_vehicle(self)\n self.spots_taken = []\n\n def take_spot(self, spot):\n self.spots_taken.append(spot)\n\n @abstractmethod\n def can_fit_in_spot(self, spot):\n pass\n\n\nclass Motorcycle(Vehicle):\n\n def __init__(self, license_plate):\n super(Motorcycle, self).__init__(VehicleSize.MOTORCYCLE, license_plate, spot_size=1)\n\n def can_fit_in_spot(self, spot):\n return True\n\n\nclass Car(Vehicle):\n\n def __init__(self, license_plate):\n super(Car, self).__init__(VehicleSize.COMPACT, license_plate, spot_size=1)\n\n def can_fit_in_spot(self, spot):\n return True if (spot.size == LARGE or spot.size == COMPACT) else False\n\n\nclass Bus(Vehicle):\n\n def __init__(self, license_plate):\n super(Bus, self).__init__(VehicleSize.LARGE, license_plate, spot_size=5)\n\n def can_fit_in_spot(self, spot):\n return True if spot.size == LARGE else False\n\n\nclass ParkingLot(object):\n\n def __init__(self, num_levels):\n self.num_levels = num_levels\n self.levels = []\n\n def park_vehicle(self, vehicle):\n for level in levels:\n if level.park_vehicle(vehicle):\n return True\n return False\n\n\nclass Level(object):\n\n SPOTS_PER_ROW = 10\n\n def __init__(self, floor, total_spots):\n self.floor = floor\n self.num_spots = total_spots\n self.available_spots = 0\n self.parking_spots = []\n\n def spot_freed(self):\n self.available_spots += 1\n\n def park_vehicle(self, vehicle):\n spot = self._find_available_spot(vehicle)\n if spot is None:\n return None\n else:\n spot.park_vehicle(vehicle)\n return spot\n\n def _find_available_spot(self, vehicle):\n \"\"\"Find an available spot where vehicle can fit, or return None\"\"\"\n # ...\n\n def _park_starting_at_spot(self, spot, vehicle):\n \"\"\"Occupy starting at spot.spot_number to vehicle.spot_size.\"\"\"\n # ...\n\n\nclass ParkingSpot(object):\n\n def __init__(self, level, row, spot_number, spot_size, vehicle_size):\n self.level = level\n self.row = row\n self.spot_number = spot_number\n self.spot_size = spot_size\n self.vehicle_size = vehicle_size\n self.vehicle = None\n\n def is_available(self):\n return True if self.vehicle is None else False\n\n def can_fit_vehicle(self, vehicle):\n if self.vehicle is not None:\n return False\n return vehicle.can_fit_in_spot(self)\n\n def park_vehicle(self, vehicle): # ...\n def remove_vehicle(self): # ...
","headings":[]}],"sourceFiles":[{"name":"parking_lot.py","url":"https://github.com/donnemartin/system-design-primer/blob/master/solutions/object_oriented_design/parking_lot/parking_lot.py","html":"from abc import ABCMeta, abstractmethod\nfrom enum import Enum\n\n\nclass VehicleSize(Enum):\n\n MOTORCYCLE = 0\n COMPACT = 1\n LARGE = 2\n\n\nclass Vehicle(metaclass=ABCMeta):\n\n def __init__(self, vehicle_size, license_plate, spot_size):\n self.vehicle_size = vehicle_size\n self.license_plate = license_plate\n self.spot_size\n self.spots_taken = []\n\n def clear_spots(self):\n for spot in self.spots_taken:\n spot.remove_vehicle(self)\n self.spots_taken = []\n\n def take_spot(self, spot):\n self.spots_taken.append(spot)\n\n @abstractmethod\n def can_fit_in_spot(self, spot):\n pass\n\n\nclass Motorcycle(Vehicle):\n\n def __init__(self, license_plate):\n super(Motorcycle, self).__init__(VehicleSize.MOTORCYCLE, license_plate, spot_size=1)\n\n def can_fit_in_spot(self, spot):\n return True\n\n\nclass Car(Vehicle):\n\n def __init__(self, license_plate):\n super(Car, self).__init__(VehicleSize.COMPACT, license_plate, spot_size=1)\n\n def can_fit_in_spot(self, spot):\n return spot.size in (VehicleSize.LARGE, VehicleSize.COMPACT)\n\n\nclass Bus(Vehicle):\n\n def __init__(self, license_plate):\n super(Bus, self).__init__(VehicleSize.LARGE, license_plate, spot_size=5)\n\n def can_fit_in_spot(self, spot):\n return spot.size == VehicleSize.LARGE\n\n\nclass ParkingLot(object):\n\n def __init__(self, num_levels):\n self.num_levels = num_levels\n self.levels = [] # List of Levels\n\n def park_vehicle(self, vehicle):\n for level in self.levels:\n if level.park_vehicle(vehicle):\n return True\n return False\n\n\nclass Level(object):\n\n SPOTS_PER_ROW = 10\n\n def __init__(self, floor, total_spots):\n self.floor = floor\n self.num_spots = total_spots\n self.available_spots = 0\n self.spots = [] # List of ParkingSpots\n\n def spot_freed(self):\n self.available_spots += 1\n\n def park_vehicle(self, vehicle):\n spot = self._find_available_spot(vehicle)\n if spot is None:\n return None\n else:\n spot.park_vehicle(vehicle)\n return spot\n\n def _find_available_spot(self, vehicle):\n \"\"\"Find an available spot where vehicle can fit, or return None\"\"\"\n pass\n\n def _park_starting_at_spot(self, spot, vehicle):\n \"\"\"Occupy starting at spot.spot_number to vehicle.spot_size.\"\"\"\n pass\n\n\nclass ParkingSpot(object):\n\n def __init__(self, level, row, spot_number, spot_size, vehicle_size):\n self.level = level\n self.row = row\n self.spot_number = spot_number\n self.spot_size = spot_size\n self.vehicle_size = vehicle_size\n self.vehicle = None\n\n def is_available(self):\n return True if self.vehicle is None else False\n\n def can_fit_vehicle(self, vehicle):\n if self.vehicle is not None:\n return False\n return vehicle.can_fit_in_spot(self)\n\n def park_vehicle(self, vehicle):\n pass\n\n def remove_vehicle(self):\n pass
"}]}