how to input a 2d matrix in c++ code example

Example 1: 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); 
    }
}

Example 2: input 2d vector c++

vector<vector<int> > d;
int val;
for(int i = 0; i < in; i++){
    vector<int> temp;
    for(int j = 0; j < in; j++){
        cin >> val;
        temp.push_back(val);
    }
    d.push_back(temp);
    temp.clear();
}