表達式：字符串下標超出範圍

Question

每當我運行我的代碼時，出現一個錯誤，指出我的字符串下標超出範圍（錯誤消息是標題）。我預計它是從使用「櫃檯」來計算總城市和平均人口。我該如何解決這個問題？我嘗試過其他方法來計算它，但都沒有工作。

void cities(istream& in, ostream& out) 
{ 
    ifstream ("cities.txt"); 
    string country, city, city2, state, lat, longi; 
    int pop; 
    int currentPop = 0; 
    int smallestPop = 0; 
    int largestPop = 0; 
    int counter = 0; 
    int sum = 0; 
    int i = 0; 
    int average = 0; 
    string largestCity; 
    string smallestCity; 
    string population; 

    readLineOfData(in, country, city, city2, state, pop, lat, longi); 
    while(!in.fail()) 
    { 
     counter++; 
     output(out, country, city, city2, state, pop, lat, longi); 


     readLineOfData(in, country, city, city2, state, pop, lat, longi); 

     population[counter] = pop; 

     if (pop < smallestPop || smallestPop == 0) 
     { 
      smallestPop = pop; 
      smallestCity = city2; 
     } 

     if (pop > largestPop || largestPop == 0) 
     { 
      largestPop = pop; 
      largestCity = city2; 
     } 

     for (int i = 0; i<counter; i++) 
     { 
      sum += population[i]; 
      average = sum/counter; 
     } 
    } 

     out << "Smallest City: " << smallestCity << endl; 
     out << "Population: " << smallestPop << endl; 
     out << endl; 
     out << "Largest City: " << largestCity << endl; 
     out << "Largest Population: " << largestPop << endl; 
     out << endl; 
     out << "Total Cities: " << i << endl; 
     out << "Average Population: " << average << endl; 
    return; 
} 

void readLineOfData(istream& in, string &country, string &city, string &city2, 
    string &state, int &pop, string &lat, string &longi) 
{ 
    getline(in, country, ','); 
    getline(in, city, ','); 
    getline(in, city2, ','); 
    getline(in, state, ','); 
    in >> pop; 
    in.ignore(200, ','); 
    getline(in, lat, ','); 
    getline(in, longi, '\n'); 

} 

void output(ostream& out, string country, string city, string city2, 
    string state, int pop, string lat, string longi) 
{ 
} 

Answer 1

聲明

string population; 

意味着​​是字符代碼序列，但你把它當作數字的序列：

population[counter] = pop; 

也是在這一點上它大小爲0，所以索引只會出錯或給出未定義的行爲。

相反，聲明​​作爲std::vector，並使用您得到

population.push_back(pop);