제출 #855202

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
855202		thaixuandang	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	363 ms	17968 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  int S, T, U, V;
  cin >> S >> T >> U >> V, S--, T--, U--, V--;
  vector<vector<pair<int, int>>> g(n);
  for (int i = 0; i < m; ++i) {
    int u, v, w;
    cin >> u >> v >> w, u--, v--;
    g[u].emplace_back(v, w);
    g[v].emplace_back(u, w);
  }

  auto dijkstra = [&](int s) {
    vector<long long> dist(n, 1e18);
    priority_queue<pair<long long, int>> pq;
    dist[s] = 0;
    pq.emplace(0, s);
    while (pq.size()) {
      auto d = -pq.top().first;
      auto u = pq.top().second;
      pq.pop();
      if (d > dist[u]) continue;
      for (auto [v, w] : g[u]) {
        if (dist[v] > dist[u] + w) {
          dist[v] = dist[u] + w;
          pq.emplace(-dist[v], v);
        }
      }
    }
    return dist;
  };

  auto solve = [&](int S, int T) {
    auto fromS = dijkstra(S);
    auto fromT = dijkstra(T);
    auto fromU = dijkstra(U);
    auto fromV = dijkstra(V);
    vector<long long> f(n, 1e18);
    // thứ tự quy hoạch động?
    // f[y] cập nhật cho f[x]
    // fromS[y] < fromS[x]
    vector<int> order(n);
    iota(order.begin(), order.end(), 0);
    sort(order.begin(), order.end(), [&](int x, int y) {
      return fromS[x] < fromS[y];
    });
    long long ans = fromU[V];
    for (auto u : order) {
      f[u] = min(f[u], fromU[u]);
      for (auto [v, w] : g[u]) {
        if (fromS[u] + w == fromS[v] && fromS[u] + w + fromT[v] == fromS[T]) {
          f[v] = min(f[v], f[u]);
        }
      }
      if (fromS[u] + fromT[u] == fromS[T]) {
        ans = min(ans, f[u] + fromV[u]);
      }
    }
    return ans;
  };

  cout << min(solve(S, T), solve(T, S)) << endl;
  return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45