Submission #878715

#	Time	Username	Problem	Language	Result	Execution time	Memory
878715		The_Samurai	Evacuation plan (IZhO18_plan)	C++17	22 / 100	4022 ms	105704 KiB

plan

#include <random>

#include "bits/stdc++.h"
using namespace std;
using ll = long long;
const int inf = 1e9;

void solve() {
    int n, m, q;
    cin >> n >> m;
    vector<vector<pair<int, int>>> g(n + 1);
    for (int i = 0; i < m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }
    vector<int> danger(n + 1, inf);
    {
        int k;
        cin >> k;
        priority_queue<pair<int, int>> pq;
        for (int i = 0; i < k; i++) {
            int root;
            cin >> root;
            pq.emplace(0, root);
            danger[root] = 0;
        }
        vector<bool> vis(n + 1);
        while (!pq.empty()) {
            auto [d, u] = pq.top();
            pq.pop();
            d = -d;
            if (vis[u]) continue;
            vis[u] = true;
            for (auto [v, w]: g[u]) {
                if (danger[v] <= d + w) continue;
                danger[v] = d + w;
                pq.emplace(-danger[v], v);
            }
        }
    }
    const int sq = min(n, 200);
    vector<int> roots(n);
    iota(roots.begin(), roots.end(), 1);
    vector ans(sq, vector(n + 1, 0));
    vector<bool> vis(n + 1);
    vector<int> all(n);
    {
        shuffle(roots.begin(), roots.end(), mt19937(random_device()()));
        while (roots.size() != sq) roots.pop_back();
        priority_queue<pair<int, int>> pq;
        for (int i = 0; i < sq; i++) {
            int root = roots[i], z = 1;
            pq.emplace(danger[root], root);
            ans[i][root] = danger[root];
            vis[root] = true;
            all[0] = root;
            while (!pq.empty()) {
                auto [d, u] = pq.top(); pq.pop();
                for (auto [v, w]: g[u]) {
                    if (vis[v]) continue;
                    ans[i][v] = min(d, danger[v]);
                    vis[v] = true;
                    all[z++] = v;
                    pq.emplace(ans[i][v], v);
                }
            }
            for (int j = 0; j < z; j++) vis[all[j]] = false;
        }
    }

    cin >> q;
    while (q--) {
        int s, t, best = 0;
        cin >> s >> t;
        for (int i = 0; i < sq; i++) best = max(best, min(ans[i][s], ans[i][t]));
        priority_queue<pair<int, int>> pq; pq.emplace(danger[s], s);
        all[0] = s;
        vis[s] = true;
        int z = 1;
        while (!pq.empty()) {
            auto [d, u] = pq.top(); pq.pop();
            bool found = false;
            for (auto [v, w]: g[u]) {
                if (z == sq) break;
                if (vis[v]) continue;
                if (v == t) {
                    best = max(best, min(d, danger[v]));
                    found = true;
                    break;
                }
                pq.emplace(min(d, danger[v]), v);
                vis[v] = true;
                all[z++] = v;
            }
            if (found) break;
        }
        for (int j = 0; j < z; j++) vis[all[j]] = false;
        cout << best << '\n';
    }
}

int main() {
    srand(time(0));
    cin.tie(0)->sync_with_stdio(false);
#ifdef sunnatov
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    int queries = 1;
//    cin >> queries;

    for (int test_case = 1; test_case <= queries; test_case++) {
#ifdef sunnatov
        cout << "Test case: " << test_case << endl;
#endif
        solve();
        cout << '\n';
    }
}

Compilation message (stderr)

plan.cpp: In function 'void solve()':
plan.cpp:51:29: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'const int' [-Wsign-compare]
   51 |         while (roots.size() != sq) roots.pop_back();
      |                ~~~~~~~~~~~~~^~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 13
• Subtask 3: 12 / 12
• Subtask 4: 0 / 19
• Subtask 5: 0 / 46