Cout不会打印我的字符串

Question

Near the bottom after calling permute my program is supposed to print the city names that have been added to my print city string, but its only printing out blanks.

as hard as this program was to make I didn't expect my print function to give me the most annoying issue.

    int main()
    {
    string cities;
    string printCity = "";
    string line;
    char command = 0;
    unsigned city = 0;
    while (getline(cin, line))
    {
        sscanf(line.c_str(), "%c %d", &command, &city);
        if (command != 'c')
            break;
        cities.push_back((unsigned char)city);
        printCity +=(city);
    }

    gFirstCity = cities[0];

    unsigned to = 0;
    unsigned from = 0;
    uint32_t cost = 0;

    sscanf(line.c_str(), "%c %d %d %d", &command, &to, &from, &cost);
    graph[to][from]=cost;
    graph[from][to]=cost;


    while (getline(cin, line))
    {
        sscanf(line.c_str(), "%c %d %d %d", &command, &to, &from, &cost);
        graph[to][from]=cost;
        graph[from][to]=cost;
    }


    permute((char*)cities.c_str()+1, 0, cities.length()-1);
    cout << "Minimum cost for the tour: ";
    cout << printCity;

    cout << " is: "<< minTour << endl;

    return EXIT_SUCCESS;



}

Answer 1

If your cities are numbered 1, 2, 3, then printcities will be a string containing three characters, of value '\\0x01' '\\0x02' and '\\0x03' . This won't print well. If you were trying to get printcities to hold "123", you either need a stringstream, or std::to_string().

Answer 2

i agree with what has been said elsewhere: concatting an int to a string isn't working the way you want it to. instead, explicitly convert city into a string first, using something like this:

// note: needs <sstream>
string int2str(int x) {
  stringstream ss;
  ss << x;
  return ss.str();
}

then modify your code just a bit:

printCity += int2str(city);