C++读取文件数据并输出处理

Question

根据文件存入数组数据，但并不是数组所有元素都存入了数据，但想要输出时只需要输出有数据的数组元素应该如何输出
int arrary[100000];
这是我存入数据的代码

void read_file(string fileName, City *array[], int l)
{
    string firstline;
    string str;
    string city_name;
    string addition;
    string PLZ;
    l = 100000;
    ifstream inFile;
    inFile.open(fileName);
    if (!inFile.is_open())
    {
        cerr << "error opening file " << fileName << endl;
    }
    else
    {
        cout << "read file \"" << fileName << "\" ... done" << endl;
        getline(inFile, firstline, '\n');
        while (inFile.good())
        {
            getline(inFile, city_name, ';');
            getline(inFile, addition, ';');
            getline(inFile, PLZ, ';');
            getline(inFile, str, '\n');
            // cout << city_name << " " << addition << " "<< PLZ <<endl;
            insertCity(city_name, addition);
            array[stoi(PLZ)] = head;
        }
        inFile.close();
    }
}

尝试输出的代码

cin >> n;
            t = n;
            while (t)
            {
                k++;
                t /= 10;
            }
            if (k >= 5)
                cout << n << " " << array[n] << endl;
            else
            {
                t = 1;
                for (int i = k; i < 5; i++)
                    t *= 10;
                n *= t;
                for (int i = n; i - n < t; i++)
                    cout << i << " " << array[i] << endl;

这样写vscode表示没什么问题，但运行时会出bug且只能输去完整的5位数

Answer 1

array不是基本类型或者没有重载<<，直接输出会报错。