railsystem.cpp

这是一个很有用的练习题

#include "RailSystem.h"

void RailSystem::reset(void) {

    // TODO: reset the data objects of the
    // City objects' contained in cities

}

RailSystem::RailSystem(string const &filename) {

    load_services(filename);
}

void RailSystem::load_services(string const &filename) {

    ifstream inf(filename.c_str());
    string from, to;
    int fee, distance;

    while ( inf.good() ) {

        // Read in the from city, to city, the fee, and distance.
        inf >> from >> to >> fee >> distance;

        if ( inf.good() ) {

            // TODO: Add entries in the cities container and
            // and services in the rail system for the new
            // cities we read in.

        }
    }

    inf.close();
}

RailSystem::~RailSystem(void) {

    // TODO: release all the City* and Service*
    // from cities and outgoing_services

}

void RailSystem::output_cheapest_route(const string& from,
                                       const string& to, ostream& out) {

    reset();
    pair<int, int> totals = calc_route(from, to);

    if (totals.first == INT_MAX) {
        out << "There is no route from " << from << " to " << to << "\n";
    } else {
        out << "The cheapest route from " << from << " to " << to << "\n";
        out << "costs " << totals.first << " euros and spans " << totals.second
        << " kilometers\n";
        cout << recover_route(to) << "\n\n";
    }
}

bool RailSystem::is_valid_city(const string& name) {

    return cities.count(name) == 1;
}

pair<int, int> RailSystem::calc_route(string from, string to) {

    priority_queue<City*, vector<City*>, Cheapest> candidates;

    // TODO: Implement Dijkstra's shortest path algorithm to
    // find the cheapest route between the cities


    // Return the total fee and total distance.
    // Return (INT_MAX, INT_MAX) if not path is found.
    if (cities[to]->visited) {
        return pair<int,int>(cities[to]->total_fee, cities[to]->total_distance);
    } else {
        return pair<int,int>(INT_MAX, INT_MAX);
    }

}

string RailSystem::recover_route(const string& city) {

    // TODO: walk backwards through the cities
    // container to recover the route we found

    return "";
}