How to use vector of vector for reading a graph?

#include <iostream>
#include <vector>
using namespace std;
void addEdge( vector<vector<int> > adj, int, int);
void print_graph(vector<vector<int> > adj);


int main()
{

    vector<vector<int> > adj;
    addEdge(adj,1,2);     // edge from node 1 to node 2
    addEdge(adj,1,3);
    addEdge(adj,1,4);
    addEdge(adj,2,3);
    addEdge(adj,3,4);
    print_graph(adj);
    return 0;
}

void addEdge(vector<vector<int> > adj, int u , int v)
{
    adj[u].push_back(v);

}

void print_graph( vector<vector<int> > adj)
{
    for( int i = 0; i < adj.size() ; i++ )
    {
        for( int j = 0 ; j < adj[i].size(); j++ )
        {
            cout<< adj[i][j];
        }
    }
}

I have written the code for reading the graph and printing it.
Prior to this for reading graph I used to use

vector<int>adj[5]; 

But I have been told that , use

`vector<vector<int> > adj`  or `list<list<int> > adj`  

I tried but I am getting error as

segmentation fault (core dump )

Can anyone help me in using vector of vector ?? Please help for list of list also.