Amazon Interview Question Design an OO parking lot

Question

Design an OO parking lot  What classes and functions will it have  It should say  full  empty and also be able to find spot for Valet parking  The lot has 3 different types of parking  regular  handicapped and compact   Thanks

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In an Object Oriented parking lot  there will be no need for attendants because the cars will  know how to park    Finding a usable car on the lot will be difficult  the most common models will either have all their moving parts exposed as public member variables  or they will be  fully encapsulated  cars with no windows or doors   The parking spaces in our OO parking lot will not match the size and shape of the cars  an  impediance mismatch  between the spaces and the cars   License tags on our lot will have a dot between each letter and digit   Handicaped parking will only be available for licenses beginning with      and licenses beginning with  m   will be towed

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public class ParkingLot        Vector lt ParkingSpace gt  vacantParkingSpaces   null      Vector lt ParkingSpace gt  fullParkingSpaces   null       int parkingSpaceCount   0       boolean isFull      boolean isEmpty       ParkingSpace findNearestVacant ParkingType type                Iterator lt ParkingSpace gt  itr   vacantParkingSpaces iterator             while itr hasNext                          ParkingSpace parkingSpace   itr next                 if parkingSpace parkingType    type                                return parkingSpace                                  return null             void parkVehicle ParkingType type  Vehicle vehicle                if  isFull                          ParkingSpace parkingSpace   findNearestVacant type                if parkingSpace    null                                parkingSpace vehicle   vehicle                  parkingSpace isVacant   false                   vacantParkingSpaces remove parkingSpace                   fullParkingSpaces add parkingSpace                    if fullParkingSpaces size      parkingSpaceCount                      isFull   true                   isEmpty   false                                     void releaseVehicle Vehicle vehicle                if  isEmpty                          Iterator lt ParkingSpace gt  itr   fullParkingSpaces iterator                 while itr hasNext                                  ParkingSpace parkingSpace   itr next                     if parkingSpace vehicle equals vehicle                                         fullParkingSpaces remove parkingSpace                       vacantParkingSpaces add parkingSpace                        parkingSpace isVacant   true                      parkingSpace vehicle   null                       if vacantParkingSpaces size      parkingSpaceCount                          isEmpty   true                       isFull   false                                                       boolean isFull                 return isFull             boolean isEmpty                 return isEmpty           public class ParkingSpace        boolean isVacant      Vehicle vehicle      ParkingType parkingType      int distance     public class Vehicle        int num     public enum ParkingType       REGULAR      HANDICAPPED      COMPACT      MAX PARKING TYPE

User · Answer

Models don t exist in isolation  The structures you d define for a simulation of cars entering a car park  an embedded system which guides you to a free space  a car parking billing system or for the automated gates ticket machines usual in car parks are all different

User · Answer

Here is a quick start to get the gears turning     ParkingLot is a class   ParkingSpace is a class   ParkingSpace has an Entrance   Entrance has a location or more specifically  distance from Entrance   ParkingLotSign is a class   ParkingLot has a ParkingLotSign   ParkingLot has a finite number of ParkingSpaces   HandicappedParkingSpace is a subclass of ParkingSpace   RegularParkingSpace is a subclass of ParkingSpace   CompactParkingSpace is a subclass of ParkingSpace   ParkingLot keeps array of ParkingSpaces  and a separate array of vacant ParkingSpaces in order of distance from its Entrance   ParkingLotSign can be told to display  full   or  empty   or  blank normal partially occupied  by calling  Full     Empty   or  Normal    Parker is a class   Parker can Park     Parker can Unpark     Valet is a subclass of Parker that can call ParkingLot FindVacantSpaceNearestEntrance    which returns a ParkingSpace   Parker has a ParkingSpace   Parker can call ParkingSpace Take   and ParkingSpace Vacate     Parker calls Entrance Entering   and Entrance Exiting   and ParkingSpace notifies ParkingLot when it is taken or vacated so that ParkingLot can determine if it is full or not   If it is newly full or newly empty or newly not full or empty  it should change the ParkingLotSign Full   or ParkingLotSign Empty   or ParkingLotSign Normal     HandicappedParker could be a subclass of Parker and CompactParker a subclass of Parker and RegularParker a subclass of Parker   might be overkill  actually    In this solution  it is possible that Parker should be renamed to be Car

User · Answer

you would need a parking lot  that holds a multi-dimensional array  specified in the constructor  of a type  space   The parking lot can keep track of how many spaces are taken via calls to functions that fill and empty spaces Space can hold an enumerated type that tells what kind of space it is  Space also has a method taken    for the valet parking  just find the first space thats open and put the car there  You will also need a Car object to put in the space  that holds whether it is a handicapped  compact  or regular vehicle    class ParkingLot       Space     spaces       ParkingLot wide  long      constructor      FindOpenSpace TypeOfCar      find first open space where type matches    enum TypeOfSpace    compact  handicapped  regular    enum TypeOfCar    compact  handicapped  regular     class Space       TypeOfSpace type      bool empty         gets and sets here        make sure car type    class car       TypeOfCar type

[oop] Amazon Interview Question: Design an OO parking lot

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