Контейнерный класс map

#include <iostream>
#include <map>
#include <vector>
#include <utility>
#include <string>
#include <iterator>
#include <algorithm>
 
struct Bus {
  size_t number;
  std::string driver;
  size_t route;
  Bus() : number(0), driver(""), route(0) {}
  Bus(size_t number_, const std::string &driver_, size_t route_)
    : number(number_), driver(driver_), route(route_) {}
  friend std::ostream &operator<<(std::ostream &stream, const Bus &bus) {
    return stream << "Bus #" << bus.number << ", driver: " << bus.driver <<
      ", route: " << bus.route << ".";
  }
};
 
class Buses {
 public:
  typedef std::map<size_t, Bus> BusMap;
  Buses() : buses() {}
  void add(const Bus &bus) {
    buses[bus.number] = bus;
  }
  size_t size() const {
    return buses.size();
  }
  template <class Compare>
  std::vector<Bus> asVector(Compare compare) {
    std::vector<Bus> result;
    for (BusMap::iterator i = buses.begin(); i != buses.end(); ++i)
      result.push_back(i->second);
    std::sort(result.begin(), result.end(), compare);
    return result;
  }
  const Bus &operator[](size_t number) {
    return buses[number];
  }
  const Bus &get(size_t number) {
    return buses[number];
  }
  size_t erase(size_t number) {
    return buses.erase(number);
  }
  void moveTo(Buses &destination, size_t number) {
    destination.add(get(number));
    erase(number);
  }
  static bool compareByNumber(const Bus &a, const Bus &b) {
    return a.number < b.number;
  }
  static bool compareByRoute(const Bus &a, const Bus &b) {
    return a.route < b.route;
  }
 private:
  BusMap buses;
};
 
std::ostream &operator<<(std::ostream &stream, const std::vector<Bus> buses) {
  std::copy(buses.begin(), buses.end(), std::ostream_iterator<Bus>(stream, "\n"));
  return stream;
}
 
int main(int argc, char *argv[]) {
  Buses inPark, onRoute;
 
  // добавление автобусов
  inPark.add(Bus(102, "A.B. Ivanov", 102));
  inPark.add(Bus(309, "C.D. Petrov", 309));
  inPark.add(Bus(23, "E.F. Sidorov", 207));
  inPark.add(Bus(27, "E.F. Sidorov", 107));
 
  // вывод
  std::cout << "In park:" << std::endl <<
    // автобусов в парке (отсортированных по номеру)
    inPark.asVector(Buses::compareByNumber) <<
    "On route:" << std::endl <<
  // и на маршруте (отсторированных по маршруту
    onRoute.asVector(Buses::compareByRoute) <<
    "========================================================" << std::endl;
 
  // из парка на маршрут
  inPark.moveTo(onRoute, 23);
  inPark.moveTo(onRoute, 102);
  inPark.moveTo(onRoute, 27);
 
  // вывод
  std::cout << "In park:" << std::endl << inPark.asVector(Buses::compareByNumber) <<
    "On route:" << std::endl << onRoute.asVector(Buses::compareByRoute) <<
    "========================================================" << std::endl;
 
  // из маршрута в парк
  onRoute.moveTo(inPark, 23);
  onRoute.moveTo(inPark, 27);
 
  // вывод
  std::cout << "In park:" << std::endl << inPark.asVector(Buses::compareByNumber) <<
    "On route:" << std::endl << onRoute.asVector(Buses::compareByRoute) <<
    "========================================================" << std::endl;
}