What is want to do!

User can enter any number of pairs.
Then I have to create a graph from the pairs where vertex is individual person and is connected to other person via edge, he is in pair with.
Then I wish to replace edge with vertex and vice versa.
What I did yet!

For unknown number of input. I have used vector to store pairs. While taking input for pairs. I have implemented a loop which gives me unique number of people in the entire list of pair.
My problem is in making a graph out of it. I have tried using vector array for that purpose. But it shows access violation error. Which I am not able to understand.
Is my code wrong or should I should some other data type like list or something else. But I have to make sure it is not of fixed length(like arrays).
Example enter image description here

My Code Yet
`
//function to add edge in graph
void addEdge(std::vector<char> adj[], char u, char v)
{
adj.push_back(v);
adj[v].push_back(u);
}

   //function to print graph
   void printGraph(std::vector<char> adj[], int V)
     {
   for (int v = 0; v < V; ++v)
   {
    std::cout << "\n Adjacency list of vertex "
    << v << "\n head ";
    for (auto x : adj[v])
        std::cout << "-> " << x;
    printf("\n");
    } 
       }

     int main()
   {    
   int numberOfUniquePeople = 0, numberOfPairs = 0, index = 0, newIndex 
   = 1;
     std::vector<char> pair; //original pair of list
     std::vector<char> uniqueElements; //unique number of people in 
         entire list
     char c = '1';
    while (c != '0')
   {
int flag = 0;
std::cout << "Enter the pair : ";
std::cin >> c; //input for first person in pair
if (c == '0')
    break;
else
    pair.push_back(c);

//start check for unique people
for (auto i = uniqueElements.begin(); i != uniqueElements.end(); i++)
{
    if(*i == c)
        flag = 1;
}
if (flag != 1)
{
    uniqueElements.push_back(c);
    numberOfUniquePeople++;
}
//end check for unique people

flag = 0;
std::cin >> c; //input for second person in the pair
pair.push_back(c);

//start check for unique people
for (auto i = uniqueElements.begin(); i != uniqueElements.end(); i++)
{
    if (*i == c)
        flag = 1;
}
if (flag != 1)
{
    uniqueElements.push_back(c);
    numberOfUniquePeople++;
}
//end check for unique people
numberOfPairs++;
}
//creating graph
std::vector<char> adj[50];
for (auto i = pair.begin(); i != pair.end(); i++)
{
        char c = *i;
        char d = *(i+1);
        addEdge(adj,c,d);
}

 printGraph(adj, 50);

 system("PAUSE");
    }

`