c++ - How to define a class which contains a variable dimension vector and how to use this class? -

i want define class, contains variable dimension vector, , defined constructor initialize it.

now problem how can use it? want use vector contain multiple of class object.

#include <iostream> #include <vector>  using namespace std;  class block { public:     long nx,ny;     vector<long> s;     block(long &nx, long &ny):nx(nx),ny(ny),s((nx+1)*(ny+1),0) {} };  int main() {     vector<block> b;     b.push_back(b(2,2));   //i believe wrong, how can this?     b.push_back(b(1,2));     for(int k=b.begin(); k<=b.end(); k++) {         for(int i=b[k].s.begin();i<=b[k].s.end();i++) {         cout<<b[k].s[i];         }     }     cout << "!!!hello world!!!" << endl; // prints !!!hello world!!!     return 0; } 

#include <iostream> #include <vector>  using namespace std;  class block { public:     long nx,ny;     vector<long> s;     block(long nx, long ny):nx(nx),ny(ny),s((nx+1)*(ny+1),0) {}         //^^^^^^^^^^^^^^^^ not necessary use inference };  int main() {     vector<block> b;     b.push_back(block(2,2));   //use block(2,2)     for(int i=0;i<b[0].s.size();i++) {     //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^the right way traversal vector         cout<<b[0].s[i];     }     cout << "!!!hello world!!!" << endl; // prints !!!hello world!!!     return 0; }