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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. vector <long long> a[100005];
  4. bool visited[100005];
  5. long long n,m;
  6. void bfs(long long i, vector<long long> a[], bool visited[])
  7. {
  8.     queue<long long> q;
  9.  
  10.     q.push(i);
  11.     visited[i] = true;
  12.     while (!q.empty())
  13.     {
  14.         long long u = q.front();
  15.         q.pop();
  16.         for (long long v : a[u])
  17.         {
  18.             if (!visited[v])
  19.             {
  20.                 visited[v] = true;
  21.                 q.push(v);
  22.             }
  23.         }
  24.     }
  25. }
  26. void input()
  27. {
  28.     cin >> n >> m;
  29.     for (long long i=1; i<=m; i++)
  30.     {
  31.         long long u,v;
  32.         cin >> u >> v;
  33.         a[u].push_back(v);
  34.         a[v].push_back(u);
  35.     }
  36. }
  37. void solve()
  38. {
  39.     for (long long i=1; i<=n; i++)
  40.     {
  41.         visited[i]=false;
  42.     }
  43.     long long cnt = 0;
  44.     for (long long i = 1; i <= n; i++)
  45.     {
  46.         if (!visited[i])
  47.         {
  48.             cnt++;
  49.             bfs(i,a,visited);
  50.         }
  51.     }
  52.     cout << cnt;
  53. }
  54. int main()
  55. {
  56.     ios_base::sync_with_stdio(0);
  57.     cin.tie(0);
  58.     input();
  59.     solve();
  60. }
  61.  
Success #stdin #stdout 0s 5896KB
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https://ideone.com/PHxnkH
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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