how to initialize 2Dvector in c++ code example

Example 1: c++ 2D vectors

int main() 
{ 
    int row = 5; // size of row 
    int colom[] = { 5, 3, 4, 2, 1 }; 
  
    vector<vector<int> > vec(row);  // Create a vector of vector with size equal to row. 
  	for (int i = 0; i < row; i++) { 
  		int col;  
        col = colom[i]; 
  		vec[i] = vector<int>(col); //Assigning the coloumn size of vector
        for (int j = 0; j < col; j++) 
            vec[i][j] = j + 1; 
    } 
  
    for (int i = 0; i < row; i++) { 
        for (int j = 0; j < vec[i].size(); j++) 
            cout << vec[i][j] << " "; 
        cout << endl; 
    } 
}

Example 2: how to take input in 2d vector in c++

std::vector<vector<int>> d;
//std::vector<int> d;
cout<<"Enter the N number of ship and port:"<<endl;
cin>>in;
cout<<"\Enter preference etc..:\n";
for(i=0; i<in; i++){ 
cout<<"ship"<<i+1<<":"<<' ';
    for(j=0; j<in; j++){
    cin>>temp;
    d.push_back(temp);// I don't know how to push_back here!!
    }
}