How can i store all my vector elements in a hash table c++

Question

Code which i Have Done##

class vehicle
{
    public:
        vehicle();
        virtual ~vehicle();
        void addVehicle();
        void deleteVehicle();
        void printvehicle(vehicle v);
        void show();
        void showleft();
        void vehcileLoad();

    protected:

    private:
    std::string pltno;
    date dt;
    lime arrive;
    lime departure;
};


int static totalvehicle=0,totalcar=0,totalamt=0,i=0,z=0;
void vehicle::addVehicle()
{

      vehicle *v = new vehicle;
      std::cin.ignore();
      std::cout<<"Enter vehicle number : ";
      std::getline(std::cin, v->pltno);
      std::cout<<"Enter arrival time in hours minutes and seconds : ";
      std::cin>>v->arrive.hh>>v->arrive.col1>>v->arrive.mm>>v->arrive.col2>>v->arrive.ss;
      std::cout<<"Enter date in day month and year: ";
      std::cin>>v->dt.day>>v->dt.sym1>>v->dt.month>>v->dt.sym2>>v->dt.year;




      veh.at(i).pltno=v->pltno;
      veh.at(i).arrive.hh=v->arrive.hh;
      veh.at(i).arrive.mm=v->arrive.mm;
      veh.at(i).arrive.ss=v->arrive.ss;
      veh.at(i).dt.day=v->dt.day;
      veh.at(i).dt.month=v->dt.month;
      veh.at(i).dt.year=v->dt.year;

What i hope to accomplish

This is part of the code i have this is also how i store data into the vector using v->pltno = ... etc I would like to know how can i store all elements within the vector into a hash table please help i am clueless how can i store all items with veh and vehleft into a hash table 1 being for vehciles in parking and 1's which have left

what would the code look like to perform such a task?

Other code of vector

std::vector<vehicle> veh(100);
std::vector<vehicle> vehleft(100);

Thank you?

Answer 1

Assuming all of your vehicle objects are stored in a std::vector<Vehicle>, using a std::unordered_map<std::string, Vehicle> is a very simple way of getting a hash table populated with the vehicles:

#include <unordered_map>
#include <vector>
#include <string>
//... 
class Vehicle
{
//...
};

void foo()
{
   std::vector<Vehicle> veh(100);
   //...
   std::unorderd_map<std::string, Vehicle> mapVehicle;
   for (auto& v : veh)
   { 
      // add the vehicle v to the hash table
      mapVehicle[v.pltNo] = v;
   }
   //...
}

Once you do that, you lookup a vehicle using the plate number:

Vehicle& v = mapVehicle["ABC123"]; // this is the vehicle with license plate ABC123

or to be safe (since using [] to do a search will add an empty entry if not found), you can check if the vehicle exists using std::unordered_map::find():

auto iter = mapVehicle.find("ABC123");
if (iter != mapVehicle.end())
{
   Vehicle& v = iter->second;
}