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  1. #include <bits/stdc++.h>
  2.  
  3. #define __QuocSensei__ int main()
  4. #define Nap_card_20k ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  5. #define Co_tat_ca_nhung_thieu_em using namespace std
  6. #define ii pair<int ,int>
  7.  
  8. Co_tat_ca_nhung_thieu_em;
  9.  
  10. const int maxn = 2e5 + 10;
  11.  
  12. int n, m, k = 2;
  13. vector<ii> adj[maxn];
  14. vector<int> dist[maxn];
  15.  
  16. void dijkstra(int s)
  17. {
  18.     priority_queue<ii, vector<ii>, greater<ii>> pq;
  19.     pq.push({0, s});
  20.     while (!pq.empty())
  21.     {
  22.         int d = pq.top().first, u = pq.top().second;
  23.         pq.pop();
  24.         if (dist[u].size() == k) continue;
  25.         if (!dist[u].empty() && d == dist[u].back()) continue;
  26.         dist[u].push_back(d);
  27.         for (ii p : adj[u])
  28.         {
  29.             int w = p.second, v = p.first;
  30.             pq.push({d + w, v});
  31.         }
  32.     }
  33. }
  34.  
  35. __QuocSensei__
  36. {
  37.     Nap_card_20k;
  38.     if (fopen("SHORTEST.INP", "r"))
  39.     {
  40.         freopen("SHORTEST.INP", "r", stdin);
  41.         freopen("SHORTEST.OUT", "w", stdout);
  42.     }
  43.     cin >> n >> m;
  44.     for (int i = 1; i <= m; i++)
  45.     {
  46.         int x, y, w;
  47.         cin >> x >> y >> w;
  48.         adj[x].push_back({y, w});
  49.     }
  50.     dijkstra(1);
  51.     if (dist[n].size() == k) cout << dist[n][k-1];
  52.     else cout << -1;
  53. }
  54.  
Success #stdin #stdout 0.01s 12912KB
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https://ideone.com/gMYE1l
language:
C++14 (gcc 8.3)
created:
4 days ago
visibility:
public

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