Submission #943346

#	Time	Username	Problem	Language	Result	Execution time	Memory
943346		GrandTiger1729	Cities (BOI16_cities)	C++17	100 / 100	3552 ms	24980 KiB

cities

#include <bits/stdc++.h>
using namespace std;

const long long INF = 1e18;
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    int n, K, m;
    cin >> n >> K >> m;
    vector<int> a(K);
    for (int i = 0; i < K; i++)
    {
        cin >> a[i];
        a[i]--;
    }
    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 i)
    {
        priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<>> pq;
        pq.emplace(0, i);
        vector<long long> dis(n, INF);
        vector<bool> vis(n);
        while (pq.size())
        {
            auto [d, u] = pq.top();
            pq.pop();
            if (vis[u])
            {
                continue;
            }
            vis[u] = 1;
            dis[u] = d;
            for (auto &[v, w] : g[u])
            {
                if (dis[v] > dis[u] + w)
                {
                    dis[v] = dis[u] + w;
                    pq.emplace(dis[v], v);
                }
            }
        }
        return dis;
    };
    auto merge = [&](const vector<long long> &b, const vector<long long> &c) -> vector<long long>
    {
        priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<>> pq;
        for (int i = 0; i < n; i++)
        {
            pq.emplace(b[i] + c[i], i);
        }
        vector<long long> ret(n, INF);
        vector<bool> vis(n);
        while (pq.size())
        {
            auto [d, u] = pq.top();
            pq.pop();
            if (vis[u])
            {
                continue;
            }
            vis[u] = 1;
            ret[u] = d;
            for (auto &[v, w] : g[u])
            {
                if (ret[v] > ret[u] + w)
                {
                    ret[v] = ret[u] + w;
                    pq.emplace(ret[v], v);
                }
            }
        }
        return ret;
    };
    sort(a.begin(), a.end());
    vector<vector<long long>> dis(K);
    for (int i = 0; i < K; i++)
    {
        dis[i] = dijkstra(a[i]);
    }
    long long ans = INF;
    vector<int> ord(K);
    iota(ord.begin(), ord.end(), 0);
    do
    {
        vector<long long> res = dis[ord[0]];
        for (int i = 1; i < K - 1; i++)
        {
            res = merge(res, dis[ord[i]]);
        }
        ans = min(ans, res[a[ord[K - 1]]]);
    }
    while (next_permutation(ord.begin(), ord.end() - 1));
    cout << ans << '\n';
    return 0;
}

• Subtask 1: 22 / 22
• Subtask 2: 14 / 14
• Subtask 3: 15 / 15
• Subtask 4: 23 / 23
• Subtask 5: 26 / 26