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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. typedef long long ll;
  4. const int MAXN = 1e5 + 7;
  5. int low[MAXN], dfstime, ans = INT_MAX, id[MAXN], scc, cnt[MAXN];
  6. vector <int> a[MAXN];
  7. int n, m;
  8. bool mark[MAXN];
  9. stack <int> st;
  10. void dfs(int u){
  11.     low[u] = id[u] = ++dfstime;
  12.     st.push(u);
  13.     for(auto v : a[u]){
  14.         if(!mark[v]){
  15.             if(!id[v]){
  16.                 dfs(v);
  17.                 low[u] = min(low[v], low[u]);
  18.             }
  19.             else low[u] = min(low[u], id[v]);
  20.         }
  21.     }
  22.     if(low[u] == id[u]){
  23.         int v;
  24.         scc++;
  25.         do{
  26.            cnt[scc]++;
  27.            v = st.top();
  28.            st.pop();
  29.            mark[v] = 1;
  30.         }while(u != v);
  31.     }
  32. }
  33.  
  34. int main(){
  35.     ios_base::sync_with_stdio(0);
  36.     cout.tie(0);
  37.     cin.tie(0);
  38.     cin >> n >> m;
  39.     for(int i = 1; i <= m; i++){
  40.         int x, y;
  41.         cin >> x >> y;
  42.         a[x].push_back(y);
  43.     }
  44.     for(int i = 1; i <= n; i++) if(!id[i]) dfs(i);
  45.     for(int i = 1; i <= scc; i++) if(cnt[i] > 1)ans = min(ans, cnt[i]);
  46.  
  47.     cout << ans;
  48. }
Success #stdin #stdout 0.01s 6580KB
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https://ideone.com/u0sJyc
language:
C++14 (gcc 8.3)
created:
5 days ago
visibility:
public

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