Submission #897934

#	Time	Username	Problem	Language	Result	Execution time	Memory
897934		avighna	Olympic Bus (JOI20_ho_t4)	C++17	37 / 100	1069 ms	7124 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const ll N = 201, M = 50001;

ll n, m;

struct Edge {
  ll u, v, i;
};

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

vector<ll> adjall[N];
bool vis[N];

void dfs(ll node) {
  if (vis[node]) {
    return;
  }
  vis[node] = true;
  for (auto &i : adjall[node]) {
    dfs(i);
  }
}

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}), adjall[u].push_back(v), adjall[v].push_back(u);
    edges[i].u = u, edges[i].v = v, edges[i].i = i;
    dist[u][v] = min(dist[u][v], c[i]);
  }

  dfs(1);
  if (!vis[n]) {
    cout << "-1\n";
    return 0;
  }

  for (ll k = 1; k <= n; ++k) {
    for (ll i = 1; i <= n; ++i) {
      for (ll j = 1; j <= n; ++j) {
        dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
      }
    }
  }

  ll ans = min((ll)1e15, dist[1][n] + dist[n][1]);
  sort(edges, edges + m, [&dist](const Edge &e1, const Edge &e2) {
    ll u1 = e1.u, u2 = e2.u, v1 = e1.v, v2 = e2.v, i1 = e1.i, i2 = e2.i;
    ll d1 = min(dist[1][n], dist[1][v1] + c[i1] + dist[u1][n]) +
            min(dist[n][1], dist[n][v1] + c[i1] + dist[u1][1]) + d[i1];
    ll d2 = min(dist[1][n], dist[1][v2] + c[i2] + dist[u2][n]) +
            min(dist[n][1], dist[n][v2] + c[i2] + dist[u2][1]) + d[i2];
    return d1 < d2;
  });
  for (ll i = 0; i < m; ++i) {
    ll u = edges[i].u, v = edges[i].v, _i = edges[i].i;
    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) {
      adj[u].erase(adj[u].find({v, _i}));
      adj[v].insert({u, _i});
      ans = min(ans, d[_i] + sssp(1)[n] + sssp(n)[1]);
      adj[v].erase(adj[v].find({u, _i}));
      adj[u].insert({v, _i});
    }
  }
  if (ans == (ll)(1e15)) {
    ans = -1;
  }
  cout << ans << "\n";
}

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