Submission #897914

#	Time	Username	Problem	Language	Result	Execution time	Memory
897914		avighna	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	1047 ms	5456 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const ll N = 201, M = 50001;

ll n, m;

multiset<pair<ll, ll>> adj[N];
ll c[M], d[M];
pair<ll, ll> edges[M];

vector<ll> sssp(ll source) {
  vector<ll> dist(n + 1, 1e15);
  dist[source] = 0;
  priority_queue<pair<ll, ll>> pq;
  pq.push({0, source});
  while (!pq.empty()) {
    ll node = pq.top().second, _dist = -pq.top().first;
    pq.pop();
    for (auto &nb : adj[node]) {
      if (dist[nb.first] > _dist + c[nb.second]) {
        dist[nb.first] = _dist + c[nb.second];
        pq.push({-dist[nb.first], nb.first});
      }
    }
  }
  return dist;
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  cin >> n >> m;
  for (ll i = 1; i <= n; ++i) {
    adj[i].clear();
  }
  vector<vector<ll>> dist(n + 1, vector<ll>(n + 1, 1e15));
  for (ll i = 1; i <= n; ++i) {
    dist[i][i] = 0;
  }
  for (ll i = 0, u, v; i < m; ++i) {
    cin >> u >> v >> c[i] >> d[i];
    adj[u].insert({v, i});
    edges[i] = {u, v};
    dist[u][v] = min(dist[u][v], c[i]);
  }

  for (ll a = 1; a <= n; ++a) {
    for (ll b = 1; b <= n; ++b) {
      for (ll c = 1; c <= n; ++c) {
        dist[a][c] = min(dist[a][c], dist[a][b] + dist[b][c]);
      }
    }
  }

  ll ans = min((ll)1e15, dist[1][n] + dist[n][1]);
  for (ll i = 0; i < m; ++i) {
    ll u = edges[i].first, v = edges[i].second;
    if (min(dist[1][n], dist[1][v] + c[i] + dist[u][n]) +
                min(dist[n][1], dist[n][v] + c[i] + dist[u][1]) + d[i] <
            ans ||
        true) {
      adj[u].erase(adj[u].find({v, i}));
      adj[v].insert({u, i});
      ans = min(ans, sssp(1)[n] + sssp(n)[1] + d[i]);
      adj[v].erase(adj[v].find({u, i}));
      adj[u].insert({v, i});
    }
  }
  if (ans == (ll)1e15) {
    ans = -1;
  }
  cout << ans << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63