iterator for 2d vector

You can use range for statement to iterate all the elements in a two-dimensional vector.

vector< vector<int> > vec;

And let's presume you have already push_back a lot of elements into vec;

for(auto& row:vec){
   for(auto& col:row){
      //do something using the element col
   }
}

Although your question is not very clear, I'm going to assume you mean a 2D vector to mean a vector of vectors:

vector< vector<int> > vvi;

Then you need to use two iterators to traverse it, the first the iterator of the "rows", the second the iterators of the "columns" in that "row":

//assuming you have a "2D" vector vvi (vector of vector of int's)
vector< vector<int> >::iterator row;
vector<int>::iterator col;
for (row = vvi.begin(); row != vvi.end(); row++) {
    for (col = row->begin(); col != row->end(); col++) {
        // do stuff ...
    }
}