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  1. #include <bits/stdc++.h>
  2. #define F first
  3. #define S second
  4. #define el cout << '\n'
  5. #define maxn 100005
  6. #define faster ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(0);
  7. #define For(i,a,b) for ( int i = a;  i <= b; i++)
  8. #define ll long long
  9. #define MOD 100000007
  10. using namespace std;
  11.  
  12. vector < int > a[maxn];
  13. int m,n,s,t,check=0;
  14. int trace[maxn];
  15. int used[maxn];
  16.  
  17. void DFS(int s, int t)
  18. {
  19.     used[s] = 1;
  20.     for(int v : a[s])
  21.     {
  22.         if (used[s] == 0)
  23.         {
  24.             trace[v] = s;
  25.             DFS(v, t);
  26.         }
  27.     }
  28.  
  29.     if (used[t] == 1)
  30.     {
  31.         check = 1;
  32.         vector <int> res;
  33.         int u = t;
  34.         while (u != s)
  35.         {
  36.             res.push_back(u);
  37.             u = trace[u];
  38.         }
  39.         res.push_back(s);
  40.         cout << res.size(); el;
  41.         reverse(res.begin(), res.end());
  42.         for(int i : res) cout << i << " ";
  43.         cout << s;
  44.     }
  45. }
  46.  
  47. int main()
  48. {
  49.     faster
  50.     cin >> n;
  51.     For(i,1,n)
  52.     {
  53.         int u, v;
  54.         cin >> u >> v;
  55.         a[u].push_back(v);
  56.         a[v].push_back(u);
  57.     }
  58.     for(int u = 1; u <= n; u++)
  59.     {
  60.         for(int v : a[u])
  61.         {
  62.             DFS(u, v);
  63.             if (check == 1) break;
  64.             else
  65.             {
  66.                 fill(trace, trace + n + 1, 0);
  67.                 fill(used, used + n + 1, 0);
  68.             }
  69.         }
  70.         if (check == 1) break;
  71.     }
  72.     if (check == 0) cout << "NO";
  73. }
  74.  
Success #stdin #stdout 0.01s 6092KB
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stdin
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Standard input is empty
stdout
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NO
https://ideone.com/XgtcI8
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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