Count Connected Component in undirected graph with adj list

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <climits>
#include <queue>
using namespace std;
const int N = 8e5, M = 4e6;
int n, m, Trace[N+1], x, y;
vector<vector<int>> Adj;
void read()
{
   cin >> n >> m;
   Adj.resize(n + 1);
   for (int i = 1; i <= m; ++ i)
   {
       cin >> x >> y;
       Adj[x].push_back(y);
       Adj[y].push_back(x);
   }
}
void DFS(int u)
{
    Trace[u] = -1;
    for (int v : Adj[u])
    {
        if (Trace[v] == 0)
        {
            Trace[v] = u;
            DFS(v);
        }
    }
}
void solve()
{
   int cnt = 0;
   for (int i = 0; i < n; ++ i)
   {
       if (Trace[i] == 0)
       {
           ++cnt;
           DFS(i);
       }
   }
   cout << cnt;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    //freopen ("TESTCODE.INP", "r", stdin);
    read();
    solve();
}