Submission #756726

#	Time	Username	Problem	Language	Result	Execution time	Memory
756726		vioalbert	Cyberland (APIO23_cyberland)	C++17	100 / 100	1366 ms	13352 KiB

cyberland

#include "cyberland.h"
#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define debug(...) __VA_ARGS__;
#else
#define debug(...)
#endif

const double INF = 1e15;

double solve(int N, int M, int K, int H, vector<int> x,
             vector<int> y, vector<int> c, vector<int> arr) {
  vector adj(N, vector<pair<int, int>>());
  for(int i = 0; i < M; i++) {
    if(x[i] != H) adj[x[i]].emplace_back(y[i], c[i]);
    if(y[i] != H) adj[y[i]].emplace_back(x[i], c[i]);
  }
  vector<int> mark(N, 0);
  const auto connected = [&](const auto &self, int u, int target) -> bool {
    if(u == target) return true;
    mark[u] = 1;
    for(auto [v, c] : adj[u]) if(!mark[v]) {
      if(self(self, v, target)) return true;
    }
    return false;
  };
  if(!connected(connected, 0, H)) {
    return -1.0;
  }
  const auto dijkstra = [&](const vector<int> &sources, vector<int> &vis,
                            vector<double> &dist) {
    using state = pair<double, int>; // dist, node
    fill(vis.begin(), vis.end(), 0);
    priority_queue<state, vector<state>, greater<state>> pq;
    for(int i : sources) pq.push({dist[i], i});
    while(!pq.empty()) {
      int u = pq.top().second; pq.pop();
      if(vis[u]) continue;
      vis[u] = 1;
      for(auto [v, c] : adj[u]) {
        if(dist[v] > dist[u] + c) {
          pq.push({dist[v] = dist[u] + c, v});
        }
      }
    }
  };
  vector<int> vis(N, 0);
  vector<int> sources{0};
  vector<double> dist(N, INF);
  for(int i : sources)
    dist[i] = 0.0;
  dijkstra(sources, vis, dist);
  for(int i = 1; i < N; i++) if(vis[i] && arr[i] == 0)
    sources.push_back(i);
  fill(dist.begin(), dist.end(), INF);
  for(int i : sources)
    dist[i] = 0.0;
  vector<double> new_dist(N);
  double ans = INF;
  for(int it = 0; it <= min(K, 95); it++) {
    if(it == 1) {
      sources.clear();
      for(int i = 0; i < N; i++) if(arr[i] != 1 && vis[i])
        sources.push_back(i);
      fill(mark.begin(), mark.end(), 0);
      bool ok = 0;
      for(int i : sources)
        ok |= connected(connected, i, H);
      if(!ok) break;
    }
    if(it > 0) {
      for(int i = 0; i < N; i++) {
        if(arr[i] == 0) new_dist[i] = 0.0;
        else if(arr[i] == 1) new_dist[i] = INF;
        else {
          new_dist[i] = INF;
          for(auto [v, c] : adj[i]) if(v != H)
            new_dist[i] = min(new_dist[i], (dist[v] + c) / 2.0);
        }
      }
      swap(dist, new_dist);
    }
    dijkstra(sources, vis, dist);
    ans = min(ans, dist[H]);
  }
  return ans;
}

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 13 / 13
• Subtask 4: 19 / 19
• Subtask 5: 7 / 7
• Subtask 6: 16 / 16
• Subtask 7: 29 / 29
• Subtask 8: 3 / 3