Inserting elements into 2D vector

To push on the vector that is an element of another vector, you simply do this

adjList[x].push_back();

If initially you do not have any values in the vector - You can push values into one vector and then push this vector into the 2D vector. For example:

  vector< vector<int> > vt1;
  vector<int> vt2;

  vt2.push_back(value);
  vt1.push_back(vt2);

If your vector is already populated then -

vt1[index].push_back(value);