declare 2d vector c++ using array code example

Example 1: declaring 2d dynamic array c++

int** arr = new int*[10]; // Number of Students
int i=0, j;
for (i; i<10; i++) 
	arr[i] = new int[5]; // Number of Courses
/*In line[1], you're creating an array which can store the addresses
  of 10 arrays. In line[4], you're allocating memories for the 
  array addresses you've stored in the array 'arr'. So it comes out 
  to be a 10 x 5 array. */

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[i].push_back(temp); 
    }
}