Graph Connectivity

#include<bits/stdc++.h>
using namespace std;
#define suni ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define ll long long
//#define tc int tc;cin>>tc;while(tc--)
#define pb push_back
#define endl "\n"
#define spc " "
#define yes "YES"
#define no "NO"
#define loop for(int i=0;i<n;i++) cin>>a[i]
#define loop1 for(int i=0;i<n;i++) cin>>b[i]
#define loop2 for(ll i=0;i<n;i++) cin>>c[i]
#define beg begin()
#define en end()
// for determining positions// lower_bound( arr.begin(), arr.end(), ele)- arr.begin();
// for determining positions// upper_bound( arr.begin(), arr.end(), ele)- arr.begin();
// for finding elements //  binary_search(arr.begin(), arr.end(), ele);
// for sorting in vector// sort(a.begin(), a.end());
 vector<int>adj[1000090];
void dfs (int node, vector<bool>&visited)
{
    visited[node] = true;
    for(int i =0; i<adj[node].size(); i++)
    {
        if( visited[adj[node][i]] == false)
        {
            dfs(adj[node][i], visited);
        }
    }
}
int main()
{
  suni;
  char c, a, b;
   int tc; cin>>tc;
   while(tc--){
    int nodes ;
    cin>>c;
    nodes = c - '0' - 16;
    cin.ignore();
    string s;
    while(getline(cin, s) && s!= "")
    {
       adj[s[0] - '0'- 16].push_back(s[1]-'0' - 16);
       adj[s[1] - '0' - 16].push_back(s[0] - '0' - 16);
}
vector<bool>visited(nodes+1, false);
    int conn = 0;
    for(int i =1; i<= nodes; i++)
    {
       if(! visited[i]){
            conn++;
            dfs(i, visited);
}
}
cout<<conn<<endl;
 if(tc) cout<<endl;
   for(int i =1; i<=nodes; i++) adj[i].clear();
}
}