number of connected components

#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main(){
    ll n,m;
    cin>>n>>m;
    vector<ll> adj[n+1];
    bool visited[n+1] = {0};
    for (ll i=1,x,y; i<=m; i++){
        cin>>x>>y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    queue<ll> q;
    ll ans=0;
    for (ll i=1; i<=n; i++){
        if (!visited[i]){
            ans++;
            visited[i]=true;
            q.push(i);
            while(!q.empty()){
                ll s=q.front();
                q.pop();
                for (auto u:adj[s]){
                    if (visited[u]) continue;
                    visited[u]=true;
                    q.push(u);
                }
            }
        }
    }
    cout<<ans<<"\n";
    return 0;
}