CareerCup

Here is my attempt at OO design. Main classes are: Elevator, Request and Person. Request is an abstract class and the classes that implement/extend it are upRequest, downRequest, emergencyExitRequest and whatever you want. ElevatorSystem is the driver class. My design closely resemble the strategy pattern as I am choosing the serviceRequest implementation at runtime.

Haven't thought about an algorithm to service requests efficiently. Will do it later.

Class Elevator{
     Private:

          Person *in; //List of persons inside the elevator
          int destinationFloor;  //Floor to which the elevator is going;
          int currentFloor;
          enum {UP, DOWN, STATIONARY} stateOfMotion;
      
     Public:
          makeRequest(Request *){
               //Handle various types of requests and reset destinationFloor and stateOfMotion based on the  request by calling serviceRequest. Hook for implementing efficient algorithm for servicing requests of different priorities.

          }

          enterElevator(Person){
               //Open door, allow to enter a person and add Person to in
          }

          exitElevator(Person){
               //Open door, allow to exit a person and remove Person from in
          } 
} 

Class Person{
     Private:
          int floor;
     
     Public:
          requestElevator(Request *){
               //Make a request to the elevator
          }

          setFloor(int floor){
               //set floor
          }
     
}


Class Request{
     Private:
          int priority;
	  timeStamp;
     
     Public{
          virtual void serviceRequest(int &destination){};
          void setPriority(){
          }
}


Class UpRequest : public Request{
//Implement go up request, this will be made typically from outside the elevator
}


Class DownRequest : public Request{
//Implement go down request, this will be made typically from outside the elevator
}

Class EmergencyExitRequest : public Request{
//Implement emergency exit request, this will be made typically from inside the elevator
}

Class DestinationFloorRequest : public Request{
//Implement go to specific floor request, this will be made typically from inside the elevator 
}


Class ElevatorSystem{
//Main class for the system
//This will be responsible for creating an Elevators and Persons
}

Sorry for taking liberties with C++ syntax.

I didn't look at the whole design, just a few things that popped out to me:
1. I would take out the "STATIONARY" from the enum and have a isMoving boolean. The reason is that the elevator may stop to let people in and out, but it still has a direction. In your design, you cannot represent this.
2. I wouldn't use a Person class nor keep track of the persons. Think about a real elevator. Does it know who or even how many persons are in it?