8.4 Design a parking lot using object-oriented principles.
LintCode上的原题，请参见我的另一篇博客Parking Lot 停车场问题。
这道题让我们实现一个停车位的数据结构，由于题目没给任何多余的信息，所以自由度很大，比如能停放什么种类的车，或是否是多层的等等。根据书中描述，这里我们做如下假设：
1. 停车场有多层，每层有多行停车位
2. 停车场可以停摩托车，小轿车和公交车
3. 停车场有摩托车位，紧凑型车位，和大型车位
4. 摩托车可以停在任何位置
5. 小轿车可以停在紧凑型车位和大型车位
6. 公交车只能停在同一行中连续的五个大型车位上，不能停在小位置上
有了这么多条件，我们就可以开始写各种类了。首先可定要有个基本类Vehicle，然后摩托车，小轿车和公交车都可以派生出来，每个派生类和基类不同的是需要的空位数不同，还有就是车型不同，那么就要把基类的判断是否能停在当前位置设为虚函数，在派生类中分别实现出来。我们还要用枚举类VehicleSize来标识车型。然后就是要有停车场类ParkingLot，层类Level，停车位类ParkingSpot，它们之间错综复杂的关系请参见下列代码：
enum class VehicleSize { Motorcycle, Compact, Large }; class Vehicle; class Level; class ParkingSpot { public: ParkingSpot(Level *lvl, int r, int n, VehicleSize s): _level(lvl), _row(r), _spotNumber(n), _spotSize(s) {} // ... bool isAvailable() { return _vehicle == nullptr; }; bool canFitVehicle(Vehicle *vehicle) {} // ... bool park(Vehicle *v) {} // ... int getRow() { return _row; } int getSpotNumber() { return _spotNumber; } void removeVehicle() {} // ... private: Vehicle *_vehicle = nullptr; VehicleSize _spotSize; int _row; int _spotNumber; Level *_level = nullptr; }; class Vehicle { public: Vehicle() {} int getSpotsNeeded() { return _spotsNeeded; } VehicleSize getSize() { return _size; } void parkInSpot(ParkingSpot s) { _parkingSpots.push_back(s); } void clearSpots() {} // ... virtual bool canFitInSpot(ParkingSpot spot) {} protected: vector<ParkingSpot> _parkingSpots; string _licensePlate; int _spotsNeeded; VehicleSize _size; }; class Bus: public Vehicle { public: Bus() { _spotsNeeded = 5; _size = VehicleSize::Large; } bool canFitInSpot(ParkingSpot spot) { } }; class Car: public Vehicle { public: Car() { _spotsNeeded = 1; _size = VehicleSize::Compact; } bool canFitInSpot(ParkingSpot spot) { } }; class Motorcycle: public Vehicle { public: Motorcycle() { _spotsNeeded = 1; _size = VehicleSize::Motorcycle; } bool canFitInSpot(ParkingSpot spot) { } }; class Level { public: Level() {} Level(int flr, int numberSpots): _floor(flr), _availableSpots(numberSpots) {} Level(const Level* lvl) { *this = *lvl; } int availableSpots() { return _availableSpots; } bool parkVehicle(Vehicle vehicle) {} // ... void spotFreed() { ++_availableSpots; } private: int _floor; vector<ParkingSpot> _spots; int _availableSpots = 0; static const int _SPOTS_PER_ROW = 10; bool parkStartingAtSpot(int num, Vehicle v) {} // ... int findAvailableSpots(Vehicle vehicle) {} // ... }; class ParkingLot { public: ParkingLot() {} // ... bool parkVehicle(Vehicle vehicle) {} // ... private: vector<Level> _levels; const int _NUM_LEVELS = 5; };
本文转自博客园Grandyang的博客，原文链接：停车场问题[CareerCup] 8.4 Parking Lot，如需转载请自行联系原博主。
